​

Token counting

• Proactively manage rate limits and costs
• Make smart model routing decisions
• Optimize prompts to be a specific length

​

How to count message tokens

​

Supported models

​

Count tokens in basic messages

import anthropic

client = anthropic.Anthropic()

response = client.messages.count_tokens(
    model="claude-sonnet-4-5",
    system="You are a scientist",
    messages=[{
        "role": "user",
        "content": "Hello, Claude"
    }],
)

print(response.json())

import Anthropic from '@anthropic-ai/sdk';

const client = new Anthropic();

const response = await client.messages.countTokens({
  model: 'claude-sonnet-4-5',
  system: 'You are a scientist',
  messages: [{
    role: 'user',
    content: 'Hello, Claude'
  }]
});

console.log(response);

curl https://api.anthropic.com/v1/messages/count_tokens \
    --header "x-api-key: $ANTHROPIC_API_KEY" \
    --header "content-type: application/json" \
    --header "anthropic-version: 2023-06-01" \
    --data '{
      "model": "claude-sonnet-4-5",
      "system": "You are a scientist",
      "messages": [{
        "role": "user",
        "content": "Hello, Claude"
      }]
    }'

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.messages.MessageCountTokensParams;
import com.anthropic.models.messages.MessageTokensCount;
import com.anthropic.models.messages.Model;

public class CountTokensExample {

    public static void main(String[] args) {
        AnthropicClient client = AnthropicOkHttpClient.fromEnv();

        MessageCountTokensParams params = MessageCountTokensParams.builder()
                .model(Model.CLAUDE_SONNET_4_20250514)
                .system("You are a scientist")
                .addUserMessage("Hello, Claude")
                .build();

        MessageTokensCount count = client.messages().countTokens(params);
        System.out.println(count);
    }
}

{ "input_tokens": 14 }

​

Count tokens in messages with tools

import anthropic

client = anthropic.Anthropic()

response = client.messages.count_tokens(
    model="claude-sonnet-4-5",
    tools=[
        {
            "name": "get_weather",
            "description": "Get the current weather in a given location",
            "input_schema": {
                "type": "object",
                "properties": {
                    "location": {
                        "type": "string",
                        "description": "The city and state, e.g. San Francisco, CA",
                    }
                },
                "required": ["location"],
            },
        }
    ],
    messages=[{"role": "user", "content": "What's the weather like in San Francisco?"}]
)

print(response.json())

import Anthropic from '@anthropic-ai/sdk';

const client = new Anthropic();

const response = await client.messages.countTokens({
  model: 'claude-sonnet-4-5',
  tools: [
    {
      name: "get_weather",
      description: "Get the current weather in a given location",
      input_schema: {
        type: "object",
        properties: {
          location: {
            type: "string",
            description: "The city and state, e.g. San Francisco, CA",
          }
        },
        required: ["location"],
      }
    }
  ],
  messages: [{ role: "user", content: "What's the weather like in San Francisco?" }]
});

console.log(response);

curl https://api.anthropic.com/v1/messages/count_tokens \
    --header "x-api-key: $ANTHROPIC_API_KEY" \
    --header "content-type: application/json" \
    --header "anthropic-version: 2023-06-01" \
    --data '{
      "model": "claude-sonnet-4-5",
      "tools": [
        {
          "name": "get_weather",
          "description": "Get the current weather in a given location",
          "input_schema": {
            "type": "object",
            "properties": {
              "location": {
                "type": "string",
                "description": "The city and state, e.g. San Francisco, CA"
              }
            },
            "required": ["location"]
          }
        }
      ],
      "messages": [
        {
          "role": "user",
          "content": "What'\''s the weather like in San Francisco?"
        }
      ]
    }'

import java.util.List;
import java.util.Map;

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.core.JsonValue;
import com.anthropic.models.messages.MessageCountTokensParams;
import com.anthropic.models.messages.MessageTokensCount;
import com.anthropic.models.messages.Model;
import com.anthropic.models.messages.Tool;
import com.anthropic.models.messages.Tool.InputSchema;

public class CountTokensWithToolsExample {

    public static void main(String[] args) {
        AnthropicClient client = AnthropicOkHttpClient.fromEnv();

        InputSchema schema = InputSchema.builder()
                .properties(JsonValue.from(Map.of(
                        "location", Map.of(
                                "type", "string",
                                "description", "The city and state, e.g. San Francisco, CA"
                        )
                )))
                .putAdditionalProperty("required", JsonValue.from(List.of("location")))
                .build();

        MessageCountTokensParams params = MessageCountTokensParams.builder()
                .model(Model.CLAUDE_SONNET_4_20250514)
                .addTool(Tool.builder()
                        .name("get_weather")
                        .description("Get the current weather in a given location")
                        .inputSchema(schema)
                        .build())
                .addUserMessage("What's the weather like in San Francisco?")
                .build();

        MessageTokensCount count = client.messages().countTokens(params);
        System.out.println(count);
    }
}

{ "input_tokens": 403 }

​

Count tokens in messages with images

#!/bin/sh

IMAGE_URL="https://upload.wikimedia.org/wikipedia/commons/a/a7/Camponotus_flavomarginatus_ant.jpg"
IMAGE_MEDIA_TYPE="image/jpeg"
IMAGE_BASE64=$(curl "$IMAGE_URL" | base64)

curl https://api.anthropic.com/v1/messages/count_tokens \
     --header "x-api-key: $ANTHROPIC_API_KEY" \
     --header "anthropic-version: 2023-06-01" \
     --header "content-type: application/json" \
     --data \
'{
    "model": "claude-sonnet-4-5",
    "messages": [
        {"role": "user", "content": [
            {"type": "image", "source": {
                "type": "base64",
                "media_type": "'$IMAGE_MEDIA_TYPE'",
                "data": "'$IMAGE_BASE64'"
            }},
            {"type": "text", "text": "Describe this image"}
        ]}
    ]
}'

import anthropic
import base64
import httpx

image_url = "https://upload.wikimedia.org/wikipedia/commons/a/a7/Camponotus_flavomarginatus_ant.jpg"
image_media_type = "image/jpeg"
image_data = base64.standard_b64encode(httpx.get(image_url).content).decode("utf-8")

client = anthropic.Anthropic()

response = client.messages.count_tokens(
    model="claude-sonnet-4-5",
    messages=[
        {
            "role": "user",
            "content": [
                {
                    "type": "image",
                    "source": {
                        "type": "base64",
                        "media_type": image_media_type,
                        "data": image_data,
                    },
                },
                {
                    "type": "text",
                    "text": "Describe this image"
                }
            ],
        }
    ],
)
print(response.json())

import Anthropic from '@anthropic-ai/sdk';

const anthropic = new Anthropic();

const image_url = "https://upload.wikimedia.org/wikipedia/commons/a/a7/Camponotus_flavomarginatus_ant.jpg"
const image_media_type = "image/jpeg"
const image_array_buffer = await ((await fetch(image_url)).arrayBuffer());
const image_data = Buffer.from(image_array_buffer).toString('base64');

const response = await anthropic.messages.countTokens({
  model: 'claude-sonnet-4-5',
  messages: [
    {
      "role": "user",
      "content": [
        {
          "type": "image",
          "source": {
            "type": "base64",
            "media_type": image_media_type,
            "data": image_data,
          },
        }
      ],
    },
    {
      "type": "text",
      "text": "Describe this image"
    }
  ]
});
console.log(response);

import java.util.Base64;
import java.util.List;

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.messages.Base64ImageSource;
import com.anthropic.models.messages.ContentBlockParam;
import com.anthropic.models.messages.ImageBlockParam;
import com.anthropic.models.messages.MessageCountTokensParams;
import com.anthropic.models.messages.MessageTokensCount;
import com.anthropic.models.messages.Model;
import com.anthropic.models.messages.TextBlockParam;

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class CountTokensImageExample {

    public static void main(String[] args) throws Exception {
        AnthropicClient client = AnthropicOkHttpClient.fromEnv();

        String imageUrl = "https://upload.wikimedia.org/wikipedia/commons/a/a7/Camponotus_flavomarginatus_ant.jpg";
        String imageMediaType = "image/jpeg";

        HttpClient httpClient = HttpClient.newHttpClient();
        HttpRequest request = HttpRequest.newBuilder()
                .uri(URI.create(imageUrl))
                .build();
        byte[] imageBytes = httpClient.send(request, HttpResponse.BodyHandlers.ofByteArray()).body();
        String imageBase64 = Base64.getEncoder().encodeToString(imageBytes);

        ContentBlockParam imageBlock = ContentBlockParam.ofImage(
                ImageBlockParam.builder()
                        .source(Base64ImageSource.builder()
                                .mediaType(Base64ImageSource.MediaType.IMAGE_JPEG)
                                .data(imageBase64)
                                .build())
                        .build());

        ContentBlockParam textBlock = ContentBlockParam.ofText(
                TextBlockParam.builder()
                        .text("Describe this image")
                        .build());

        MessageCountTokensParams params = MessageCountTokensParams.builder()
                .model(Model.CLAUDE_SONNET_4_20250514)
                .addUserMessageOfBlockParams(List.of(imageBlock, textBlock))
                .build();

        MessageTokensCount count = client.messages().countTokens(params);
        System.out.println(count);
    }
}

{ "input_tokens": 1551 }

​

Count tokens in messages with extended thinking

curl https://api.anthropic.com/v1/messages/count_tokens \
    --header "x-api-key: $ANTHROPIC_API_KEY" \
    --header "content-type: application/json" \
    --header "anthropic-version: 2023-06-01" \
    --data '{
      "model": "claude-sonnet-4-5",
      "thinking": {
        "type": "enabled",
        "budget_tokens": 16000
      },
      "messages": [
        {
          "role": "user",
          "content": "Are there an infinite number of prime numbers such that n mod 4 == 3?"
        },
        {
          "role": "assistant",
          "content": [
            {
              "type": "thinking",
              "thinking": "This is a nice number theory question. Lets think about it step by step...",
              "signature": "EuYBCkQYAiJAgCs1le6/Pol5Z4/JMomVOouGrWdhYNsH3ukzUECbB6iWrSQtsQuRHJID6lWV..."
            },
            {
              "type": "text",
              "text": "Yes, there are infinitely many prime numbers p such that p mod 4 = 3..."
            }
          ]
        },
        {
          "role": "user",
          "content": "Can you write a formal proof?"
        }
      ]
    }'

import anthropic

client = anthropic.Anthropic()

response = client.messages.count_tokens(
    model="claude-sonnet-4-5",
    thinking={
        "type": "enabled",
        "budget_tokens": 16000
    },
    messages=[
        {
            "role": "user",
            "content": "Are there an infinite number of prime numbers such that n mod 4 == 3?"
        },
        {
            "role": "assistant",
            "content": [
                {
                    "type": "thinking",
                    "thinking": "This is a nice number theory question. Let's think about it step by step...",
                    "signature": "EuYBCkQYAiJAgCs1le6/Pol5Z4/JMomVOouGrWdhYNsH3ukzUECbB6iWrSQtsQuRHJID6lWV..."
                },
                {
                  "type": "text",
                  "text": "Yes, there are infinitely many prime numbers p such that p mod 4 = 3..."
                }
            ]
        },
        {
            "role": "user",
            "content": "Can you write a formal proof?"
        }
    ]
)

print(response.json())

import Anthropic from '@anthropic-ai/sdk';

const client = new Anthropic();

const response = await client.messages.countTokens({
  model: 'claude-sonnet-4-5',
  thinking: {
    'type': 'enabled',
    'budget_tokens': 16000
  },
  messages: [
    {
      'role': 'user',
      'content': 'Are there an infinite number of prime numbers such that n mod 4 == 3?'
    },
    {
      'role': 'assistant',
      'content': [
        {
          'type': 'thinking',
          'thinking': "This is a nice number theory question. Let's think about it step by step...",
          'signature': 'EuYBCkQYAiJAgCs1le6/Pol5Z4/JMomVOouGrWdhYNsH3ukzUECbB6iWrSQtsQuRHJID6lWV...'
        },
        {
          'type': 'text',
          'text': 'Yes, there are infinitely many prime numbers p such that p mod 4 = 3...',
        }
      ]
    },
    {
      'role': 'user',
      'content': 'Can you write a formal proof?'
    }
  ]
});

console.log(response);

import java.util.List;

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.messages.ContentBlockParam;
import com.anthropic.models.messages.MessageCountTokensParams;
import com.anthropic.models.messages.MessageTokensCount;
import com.anthropic.models.messages.Model;
import com.anthropic.models.messages.TextBlockParam;
import com.anthropic.models.messages.ThinkingBlockParam;

public class CountTokensThinkingExample {

    public static void main(String[] args) {
        AnthropicClient client = AnthropicOkHttpClient.fromEnv();

        List<ContentBlockParam> assistantBlocks = List.of(
                ContentBlockParam.ofThinking(ThinkingBlockParam.builder()
                        .thinking("This is a nice number theory question. Let's think about it step by step...")
                        .signature("EuYBCkQYAiJAgCs1le6/Pol5Z4/JMomVOouGrWdhYNsH3ukzUECbB6iWrSQtsQuRHJID6lWV...")
                        .build()),
                ContentBlockParam.ofText(TextBlockParam.builder()
                        .text("Yes, there are infinitely many prime numbers p such that p mod 4 = 3...")
                        .build())
        );

        MessageCountTokensParams params = MessageCountTokensParams.builder()
                .model(Model.CLAUDE_SONNET_4_20250514)
                .enabledThinking(16000)
                .addUserMessage("Are there an infinite number of prime numbers such that n mod 4 == 3?")
                .addAssistantMessageOfBlockParams(assistantBlocks)
                .addUserMessage("Can you write a formal proof?")
                .build();

        MessageTokensCount count = client.messages().countTokens(params);
        System.out.println(count);
    }
}

{ "input_tokens": 88 }

​

Count tokens in messages with PDFs

curl https://api.anthropic.com/v1/messages/count_tokens \
    --header "x-api-key: $ANTHROPIC_API_KEY" \
    --header "content-type: application/json" \
    --header "anthropic-version: 2023-06-01" \
    --data '{
      "model": "claude-sonnet-4-5",
      "messages": [{
        "role": "user",
        "content": [
          {
            "type": "document",
            "source": {
              "type": "base64",
              "media_type": "application/pdf",
              "data": "'$(base64 -i document.pdf)'"
            }
          },
          {
            "type": "text",
            "text": "Please summarize this document."
          }
        ]
      }]
    }'

import base64
import anthropic

client = anthropic.Anthropic()

with open("document.pdf", "rb") as pdf_file:
    pdf_base64 = base64.standard_b64encode(pdf_file.read()).decode("utf-8")

response = client.messages.count_tokens(
    model="claude-sonnet-4-5",
    messages=[{
        "role": "user",
        "content": [
            {
                "type": "document",
                "source": {
                    "type": "base64",
                    "media_type": "application/pdf",
                    "data": pdf_base64
                }
            },
            {
                "type": "text",
                "text": "Please summarize this document."
            }
        ]
    }]
)

print(response.json())

import Anthropic from '@anthropic-ai/sdk';
import { readFileSync } from 'fs';

const client = new Anthropic();

const pdfBase64 = readFileSync('document.pdf', { encoding: 'base64' });

const response = await client.messages.countTokens({
  model: 'claude-sonnet-4-5',
  messages: [{
    role: 'user',
    content: [
      {
        type: 'document',
        source: {
          type: 'base64',
          media_type: 'application/pdf',
          data: pdfBase64
        }
      },
      {
        type: 'text',
        text: 'Please summarize this document.'
      }
    ]
  }]
});

console.log(response);

import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Base64;
import java.util.List;

import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.messages.Base64PdfSource;
import com.anthropic.models.messages.ContentBlockParam;
import com.anthropic.models.messages.DocumentBlockParam;
import com.anthropic.models.messages.MessageCountTokensParams;
import com.anthropic.models.messages.MessageTokensCount;
import com.anthropic.models.messages.Model;
import com.anthropic.models.messages.TextBlockParam;

public class CountTokensPdfExample {

    public static void main(String[] args) throws Exception {
        AnthropicClient client = AnthropicOkHttpClient.fromEnv();

        byte[] fileBytes = Files.readAllBytes(Path.of("document.pdf"));
        String pdfBase64 = Base64.getEncoder().encodeToString(fileBytes);

        ContentBlockParam documentBlock = ContentBlockParam.ofDocument(
                DocumentBlockParam.builder()
                        .source(Base64PdfSource.builder()
                                .mediaType(Base64PdfSource.MediaType.APPLICATION_PDF)
                                .data(pdfBase64)
                                .build())
                        .build());

        ContentBlockParam textBlock = ContentBlockParam.ofText(
                TextBlockParam.builder()
                        .text("Please summarize this document.")
                        .build());

        MessageCountTokensParams params = MessageCountTokensParams.builder()
                .model(Model.CLAUDE_SONNET_4_20250514)
                .addUserMessageOfBlockParams(List.of(documentBlock, textBlock))
                .build();

        MessageTokensCount count = client.messages().countTokens(params);
        System.out.println(count);
    }
}

{ "input_tokens": 2188 }

​

Pricing and rate limits

​

FAQ

​

Count Tokens

​

Parameters

• body: MessageCountTokensParams
  • messages: Array<MessageParam> Input messages. Our models are trained to operate on alternating user and assistant conversational turns. When creating a new Message, you specify the prior conversational turns with the messages parameter, and the model then generates the next Message in the conversation. Consecutive user or assistant turns in your request will be combined into a single turn. Each input message must be an object with a role and content. You can specify a single user-role message, or you can include multiple user and assistant messages. If the final message uses the assistant role, the response content will continue immediately from the content in that message. This can be used to constrain part of the model’s response. Example with a single user message:
    [{"role": "user", "content": "Hello, Claude"}]
    
    Example with multiple conversational turns:
    [
      {"role": "user", "content": "Hello there."},
      {"role": "assistant", "content": "Hi, I'm Claude. How can I help you?"},
      {"role": "user", "content": "Can you explain LLMs in plain English?"},
    ]
    
    Example with a partially-filled response from Claude:
    [
      {"role": "user", "content": "What's the Greek name for Sun? (A) Sol (B) Helios (C) Sun"},
      {"role": "assistant", "content": "The best answer is ("},
    ]
    
    Each input message content may be either a single string or an array of content blocks, where each block has a specific type. Using a string for content is shorthand for an array of one content block of type "text". The following input messages are equivalent:
    {"role": "user", "content": "Hello, Claude"}
    
    {"role": "user", "content": [{"type": "text", "text": "Hello, Claude"}]}
    
    See input examples. Note that if you want to include a system prompt, you can use the top-level system parameter — there is no "system" role for input messages in the Messages API. There is a limit of 100,000 messages in a single request.
    • content: string | Array<ContentBlockParam>
      • string
      • Array<ContentBlockParam>
        • TextBlockParam
          • text: string
          • type: "text"
            • "text"
          • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
            • type: "ephemeral"
              • "ephemeral"
            • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
              • 5m: 5 minutes
              • 1h: 1 hour
              Defaults to 5m.
              • "5m"
              • "1h"
          • citations?: Array<TextCitationParam> | null
            • CitationCharLocationParam
              • cited_text: string
              • document_index: number
              • document_title: string | null
              • end_char_index: number
              • start_char_index: number
              • type: "char_location"
                • "char_location"
            • CitationPageLocationParam
              • cited_text: string
              • document_index: number
              • document_title: string | null
              • end_page_number: number
              • start_page_number: number
              • type: "page_location"
                • "page_location"
            • CitationContentBlockLocationParam
              • cited_text: string
              • document_index: number
              • document_title: string | null
              • end_block_index: number
              • start_block_index: number
              • type: "content_block_location"
                • "content_block_location"
            • CitationWebSearchResultLocationParam
              • cited_text: string
              • encrypted_index: string
              • title: string | null
              • type: "web_search_result_location"
                • "web_search_result_location"
              • url: string
            • CitationSearchResultLocationParam
              • cited_text: string
              • end_block_index: number
              • search_result_index: number
              • source: string
              • start_block_index: number
              • title: string | null
              • type: "search_result_location"
                • "search_result_location"
        • ImageBlockParam
          • source: Base64ImageSource | URLImageSource
            • Base64ImageSource
              • data: string
              • media_type: "image/jpeg" | "image/png" | "image/gif" | "image/webp"
                • "image/jpeg"
                • "image/png"
                • "image/gif"
                • "image/webp"
              • type: "base64"
                • "base64"
            • URLImageSource
              • type: "url"
                • "url"
              • url: string
          • type: "image"
            • "image"
          • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
            • type: "ephemeral"
              • "ephemeral"
            • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
              • 5m: 5 minutes
              • 1h: 1 hour
              Defaults to 5m.
              • "5m"
              • "1h"
        • DocumentBlockParam
          • source: Base64PDFSource | PlainTextSource | ContentBlockSource | URLPDFSource
            • Base64PDFSource
              • data: string
              • media_type: "application/pdf"
                • "application/pdf"
              • type: "base64"
                • "base64"
            • PlainTextSource
              • data: string
              • media_type: "text/plain"
                • "text/plain"
              • type: "text"
                • "text"
            • ContentBlockSource
              • content: string | Array<ContentBlockSourceContent>
                • string
                • Array<ContentBlockSourceContent>
                  • TextBlockParam
                    • text: string
                    • type: "text"
                      • "text"
                    • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
                      • type: "ephemeral"
                        • "ephemeral"
                      • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
                        • 5m: 5 minutes
                        • 1h: 1 hour
                        Defaults to 5m.
                        • "5m"
                        • "1h"
                    • citations?: Array<TextCitationParam> | null
                      • CitationCharLocationParam
                        • cited_text: string
                        • document_index: number
                        • document_title: string | null
                        • end_char_index: number
                        • start_char_index: number
                        • type: "char_location"
                          • "char_location"
                      • CitationPageLocationParam
                        • cited_text: string
                        • document_index: number
                        • document_title: string | null
                        • end_page_number: number
                        • start_page_number: number
                        • type: "page_location"
                          • "page_location"
                      • CitationContentBlockLocationParam
                        • cited_text: string
                        • document_index: number
                        • document_title: string | null
                        • end_block_index: number
                        • start_block_index: number
                        • type: "content_block_location"
                          • "content_block_location"
                      • CitationWebSearchResultLocationParam
                        • cited_text: string
                        • encrypted_index: string
                        • title: string | null
                        • type: "web_search_result_location"
                          • "web_search_result_location"
                        • url: string
                      • CitationSearchResultLocationParam
                        • cited_text: string
                        • end_block_index: number
                        • search_result_index: number
                        • source: string
                        • start_block_index: number
                        • title: string | null
                        • type: "search_result_location"
                          • "search_result_location"
                  • ImageBlockParam
                    • source: Base64ImageSource | URLImageSource
                      • Base64ImageSource
                        • data: string
                        • media_type: "image/jpeg" | "image/png" | "image/gif" | "image/webp"
                          • "image/jpeg"
                          • "image/png"
                          • "image/gif"
                          • "image/webp"
                        • type: "base64"
                          • "base64"
                      • URLImageSource
                        • type: "url"
                          • "url"
                        • url: string
                    • type: "image"
                      • "image"
                    • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
                      • type: "ephemeral"
                        • "ephemeral"
                      • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
                        • 5m: 5 minutes
                        • 1h: 1 hour
                        Defaults to 5m.
                        • "5m"
                        • "1h"
              • type: "content"
                • "content"
            • URLPDFSource
              • type: "url"
                • "url"
              • url: string
          • type: "document"
            • "document"
          • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
            • type: "ephemeral"
              • "ephemeral"
            • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
              • 5m: 5 minutes
              • 1h: 1 hour
              Defaults to 5m.
              • "5m"
              • "1h"
          • citations?: CitationsConfigParam | null
            • enabled?: boolean
          • context?: string | null
          • title?: string | null
        • SearchResultBlockParam
          • content: Array<TextBlockParam>
            • text: string
            • type: "text"
              • "text"
            • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
              • type: "ephemeral"
                • "ephemeral"
              • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
                • 5m: 5 minutes
                • 1h: 1 hour
                Defaults to 5m.
                • "5m"
                • "1h"
            • citations?: Array<TextCitationParam> | null
              • CitationCharLocationParam
                • cited_text: string
                • document_index: number
                • document_title: string | null
                • end_char_index: number
                • start_char_index: number
                • type: "char_location"
                  • "char_location"
              • CitationPageLocationParam
                • cited_text: string
                • document_index: number
                • document_title: string | null
                • end_page_number: number
                • start_page_number: number
                • type: "page_location"
                  • "page_location"
              • CitationContentBlockLocationParam
                • cited_text: string
                • document_index: number
                • document_title: string | null
                • end_block_index: number
                • start_block_index: number
                • type: "content_block_location"
                  • "content_block_location"
              • CitationWebSearchResultLocationParam
                • cited_text: string
                • encrypted_index: string
                • title: string | null
                • type: "web_search_result_location"
                  • "web_search_result_location"
                • url: string
              • CitationSearchResultLocationParam
                • cited_text: string
                • end_block_index: number
                • search_result_index: number
                • source: string
                • start_block_index: number
                • title: string | null
                • type: "search_result_location"
                  • "search_result_location"
          • source: string
          • title: string
          • type: "search_result"
            • "search_result"
          • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
            • type: "ephemeral"
              • "ephemeral"
            • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
              • 5m: 5 minutes
              • 1h: 1 hour
              Defaults to 5m.
              • "5m"
              • "1h"
          • citations?: CitationsConfigParam
            • enabled?: boolean
        • ThinkingBlockParam
          • signature: string
          • thinking: string
          • type: "thinking"
            • "thinking"
        • RedactedThinkingBlockParam
          • data: string
          • type: "redacted_thinking"
            • "redacted_thinking"
        • ToolUseBlockParam
          • id: string
          • input: Record<string, unknown>
          • name: string
          • type: "tool_use"
            • "tool_use"
          • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
            • type: "ephemeral"
              • "ephemeral"
            • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
              • 5m: 5 minutes
              • 1h: 1 hour
              Defaults to 5m.
              • "5m"
              • "1h"
        • ToolResultBlockParam
          • tool_use_id: string
          • type: "tool_result"
            • "tool_result"
          • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
            • type: "ephemeral"
              • "ephemeral"
            • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
              • 5m: 5 minutes
              • 1h: 1 hour
              Defaults to 5m.
              • "5m"
              • "1h"
          • content?: string | Array<TextBlockParam | ImageBlockParam | SearchResultBlockParam | DocumentBlockParam>
            • string
            • Array<TextBlockParam | ImageBlockParam | SearchResultBlockParam | DocumentBlockParam>
              • TextBlockParam
                • text: string
                • type: "text"
                  • "text"
                • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
                  • type: "ephemeral"
                    • "ephemeral"
                  • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
                    • 5m: 5 minutes
                    • 1h: 1 hour
                    Defaults to 5m.
                    • "5m"
                    • "1h"
                • citations?: Array<TextCitationParam> | null
                  • CitationCharLocationParam
                    • cited_text: string
                    • document_index: number
                    • document_title: string | null
                    • end_char_index: number
                    • start_char_index: number
                    • type: "char_location"
                      • "char_location"
                  • CitationPageLocationParam
                    • cited_text: string
                    • document_index: number
                    • document_title: string | null
                    • end_page_number: number
                    • start_page_number: number
                    • type: "page_location"
                      • "page_location"
                  • CitationContentBlockLocationParam
                    • cited_text: string
                    • document_index: number
                    • document_title: string | null
                    • end_block_index: number
                    • start_block_index: number
                    • type: "content_block_location"
                      • "content_block_location"
                  • CitationWebSearchResultLocationParam
                    • cited_text: string
                    • encrypted_index: string
                    • title: string | null
                    • type: "web_search_result_location"
                      • "web_search_result_location"
                    • url: string
                  • CitationSearchResultLocationParam
                    • cited_text: string
                    • end_block_index: number
                    • search_result_index: number
                    • source: string
                    • start_block_index: number
                    • title: string | null
                    • type: "search_result_location"
                      • "search_result_location"
              • ImageBlockParam
                • source: Base64ImageSource | URLImageSource
                  • Base64ImageSource
                    • data: string
                    • media_type: "image/jpeg" | "image/png" | "image/gif" | "image/webp"
                      • "image/jpeg"
                      • "image/png"
                      • "image/gif"
                      • "image/webp"
                    • type: "base64"
                      • "base64"
                  • URLImageSource
                    • type: "url"
                      • "url"
                    • url: string
                • type: "image"
                  • "image"
                • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
                  • type: "ephemeral"
                    • "ephemeral"
                  • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
                    • 5m: 5 minutes
                    • 1h: 1 hour
                    Defaults to 5m.
                    • "5m"
                    • "1h"
              • SearchResultBlockParam
                • content: Array<TextBlockParam>
                  • text: string
                  • type: "text"
                    • "text"
                  • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
                    • type: "ephemeral"
                      • "ephemeral"
                    • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
                      • 5m: 5 minutes
                      • 1h: 1 hour
                      Defaults to 5m.
                      • "5m"
                      • "1h"
                  • citations?: Array<TextCitationParam> | null
                    • CitationCharLocationParam
                      • cited_text: string
                      • document_index: number
                      • document_title: string | null
                      • end_char_index: number
                      • start_char_index: number
                      • type: "char_location"
                        • "char_location"
                    • CitationPageLocationParam
                      • cited_text: string
                      • document_index: number
                      • document_title: string | null
                      • end_page_number: number
                      • start_page_number: number
                      • type: "page_location"
                        • "page_location"
                    • CitationContentBlockLocationParam
                      • cited_text: string
                      • document_index: number
                      • document_title: string | null
                      • end_block_index: number
                      • start_block_index: number
                      • type: "content_block_location"
                        • "content_block_location"
                    • CitationWebSearchResultLocationParam
                      • cited_text: string
                      • encrypted_index: string
                      • title: string | null
                      • type: "web_search_result_location"
                        • "web_search_result_location"
                      • url: string
                    • CitationSearchResultLocationParam
                      • cited_text: string
                      • end_block_index: number
                      • search_result_index: number
                      • source: string
                      • start_block_index: number
                      • title: string | null
                      • type: "search_result_location"
                        • "search_result_location"
                • source: string
                • title: string
                • type: "search_result"
                  • "search_result"
                • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
                  • type: "ephemeral"
                    • "ephemeral"
                  • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
                    • 5m: 5 minutes
                    • 1h: 1 hour
                    Defaults to 5m.
                    • "5m"
                    • "1h"
                • citations?: CitationsConfigParam
                  • enabled?: boolean
              • DocumentBlockParam
                • source: Base64PDFSource | PlainTextSource | ContentBlockSource | URLPDFSource
                  • Base64PDFSource
                    • data: string
                    • media_type: "application/pdf"
                      • "application/pdf"
                    • type: "base64"
                      • "base64"
                  • PlainTextSource
                    • data: string
                    • media_type: "text/plain"
                      • "text/plain"
                    • type: "text"
                      • "text"
                  • ContentBlockSource
                    • content: string | Array<ContentBlockSourceContent>
                      • string
                      • Array<ContentBlockSourceContent>
                        • TextBlockParam
                          • text: string
                          • type: "text"
                            • "text"
                          • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
                            • type: "ephemeral"
                              • "ephemeral"
                            • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
                              • 5m: 5 minutes
                              • 1h: 1 hour
                              Defaults to 5m.
                              • "5m"
                              • "1h"
                          • citations?: Array<TextCitationParam> | null
                            • CitationCharLocationParam
                              • cited_text: string
                              • document_index: number
                              • document_title: string | null
                              • end_char_index: number
                              • start_char_index: number
                              • type: "char_location"
                                • "char_location"
                            • CitationPageLocationParam
                              • cited_text: string
                              • document_index: number
                              • document_title: string | null
                              • end_page_number: number
                              • start_page_number: number
                              • type: "page_location"
                                • "page_location"
                            • CitationContentBlockLocationParam
                              • cited_text: string
                              • document_index: number
                              • document_title: string | null
                              • end_block_index: number
                              • start_block_index: number
                              • type: "content_block_location"
                                • "content_block_location"
                            • CitationWebSearchResultLocationParam
                              • cited_text: string
                              • encrypted_index: string
                              • title: string | null
                              • type: "web_search_result_location"
                                • "web_search_result_location"
                              • url: string
                            • CitationSearchResultLocationParam
                              • cited_text: string
                              • end_block_index: number
                              • search_result_index: number
                              • source: string
                              • start_block_index: number
                              • title: string | null
                              • type: "search_result_location"
                                • "search_result_location"
                        • ImageBlockParam
                          • source: Base64ImageSource | URLImageSource
                            • Base64ImageSource
                              • data: string
                              • media_type: "image/jpeg" | "image/png" | "image/gif" | "image/webp"
                                • "image/jpeg"
                                • "image/png"
                                • "image/gif"
                                • "image/webp"
                              • type: "base64"
                                • "base64"
                            • URLImageSource
                              • type: "url"
                                • "url"
                              • url: string
                          • type: "image"
                            • "image"
                          • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
                            • type: "ephemeral"
                              • "ephemeral"
                            • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
                              • 5m: 5 minutes
                              • 1h: 1 hour
                              Defaults to 5m.
                              • "5m"
                              • "1h"
                    • type: "content"
                      • "content"
                  • URLPDFSource
                    • type: "url"
                      • "url"
                    • url: string
                • type: "document"
                  • "document"
                • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
                  • type: "ephemeral"
                    • "ephemeral"
                  • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
                    • 5m: 5 minutes
                    • 1h: 1 hour
                    Defaults to 5m.
                    • "5m"
                    • "1h"
                • citations?: CitationsConfigParam | null
                  • enabled?: boolean
                • context?: string | null
                • title?: string | null
          • is_error?: boolean
        • ServerToolUseBlockParam
          • id: string
          • input: Record<string, unknown>
          • name: "web_search"
            • "web_search"
          • type: "server_tool_use"
            • "server_tool_use"
          • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
            • type: "ephemeral"
              • "ephemeral"
            • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
              • 5m: 5 minutes
              • 1h: 1 hour
              Defaults to 5m.
              • "5m"
              • "1h"
        • WebSearchToolResultBlockParam
          • content: WebSearchToolResultBlockParamContent
            • Array<WebSearchResultBlockParam>
              • encrypted_content: string
              • title: string
              • type: "web_search_result"
                • "web_search_result"
              • url: string
              • page_age?: string | null
            • WebSearchToolRequestError
              • error_code: "invalid_tool_input" | "unavailable" | "max_uses_exceeded" | 2 more
                • "invalid_tool_input"
                • "unavailable"
                • "max_uses_exceeded"
                • "too_many_requests"
                • "query_too_long"
              • type: "web_search_tool_result_error"
                • "web_search_tool_result_error"
          • tool_use_id: string
          • type: "web_search_tool_result"
            • "web_search_tool_result"
          • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
            • type: "ephemeral"
              • "ephemeral"
            • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
              • 5m: 5 minutes
              • 1h: 1 hour
              Defaults to 5m.
              • "5m"
              • "1h"
    • role: "user" | "assistant"
      • "user"
      • "assistant"
  • model: Model The model that will complete your prompt. See models for additional details and options.
    • "claude-opus-4-5-20251101" | "claude-opus-4-5" | "claude-3-7-sonnet-latest" | 17 more
      • "claude-opus-4-5-20251101" Premium model combining maximum intelligence with practical performance
      • "claude-opus-4-5" Premium model combining maximum intelligence with practical performance
      • "claude-3-7-sonnet-latest" High-performance model with early extended thinking
      • "claude-3-7-sonnet-20250219" High-performance model with early extended thinking
      • "claude-3-5-haiku-latest" Fastest and most compact model for near-instant responsiveness
      • "claude-3-5-haiku-20241022" Our fastest model
      • "claude-haiku-4-5" Hybrid model, capable of near-instant responses and extended thinking
      • "claude-haiku-4-5-20251001" Hybrid model, capable of near-instant responses and extended thinking
      • "claude-sonnet-4-20250514" High-performance model with extended thinking
      • "claude-sonnet-4-0" High-performance model with extended thinking
      • "claude-4-sonnet-20250514" High-performance model with extended thinking
      • "claude-sonnet-4-5" Our best model for real-world agents and coding
      • "claude-sonnet-4-5-20250929" Our best model for real-world agents and coding
      • "claude-opus-4-0" Our most capable model
      • "claude-opus-4-20250514" Our most capable model
      • "claude-4-opus-20250514" Our most capable model
      • "claude-opus-4-1-20250805" Our most capable model
      • "claude-3-opus-latest" Excels at writing and complex tasks
      • "claude-3-opus-20240229" Excels at writing and complex tasks
      • "claude-3-haiku-20240307" Our previous most fast and cost-effective
    • (string & {})
  • system?: string | Array<TextBlockParam> System prompt. A system prompt is a way of providing context and instructions to Claude, such as specifying a particular goal or role. See our guide to system prompts.
    • string
    • Array<TextBlockParam>
      • text: string
      • type: "text"
        • "text"
      • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
        • type: "ephemeral"
          • "ephemeral"
        • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
          • 5m: 5 minutes
          • 1h: 1 hour
          Defaults to 5m.
          • "5m"
          • "1h"
      • citations?: Array<TextCitationParam> | null
        • CitationCharLocationParam
          • cited_text: string
          • document_index: number
          • document_title: string | null
          • end_char_index: number
          • start_char_index: number
          • type: "char_location"
            • "char_location"
        • CitationPageLocationParam
          • cited_text: string
          • document_index: number
          • document_title: string | null
          • end_page_number: number
          • start_page_number: number
          • type: "page_location"
            • "page_location"
        • CitationContentBlockLocationParam
          • cited_text: string
          • document_index: number
          • document_title: string | null
          • end_block_index: number
          • start_block_index: number
          • type: "content_block_location"
            • "content_block_location"
        • CitationWebSearchResultLocationParam
          • cited_text: string
          • encrypted_index: string
          • title: string | null
          • type: "web_search_result_location"
            • "web_search_result_location"
          • url: string
        • CitationSearchResultLocationParam
          • cited_text: string
          • end_block_index: number
          • search_result_index: number
          • source: string
          • start_block_index: number
          • title: string | null
          • type: "search_result_location"
            • "search_result_location"
  • thinking?: ThinkingConfigParam Configuration for enabling Claude’s extended thinking. When enabled, responses include thinking content blocks showing Claude’s thinking process before the final answer. Requires a minimum budget of 1,024 tokens and counts towards your max_tokens limit. See extended thinking for details.
    • ThinkingConfigEnabled
      • budget_tokens: number Determines how many tokens Claude can use for its internal reasoning process. Larger budgets can enable more thorough analysis for complex problems, improving response quality. Must be ≥1024 and less than max_tokens. See extended thinking for details.
      • type: "enabled"
        • "enabled"
    • ThinkingConfigDisabled
      • type: "disabled"
        • "disabled"
  • tool_choice?: ToolChoice How the model should use the provided tools. The model can use a specific tool, any available tool, decide by itself, or not use tools at all.
    • ToolChoiceAuto The model will automatically decide whether to use tools.
      • type: "auto"
        • "auto"
      • disable_parallel_tool_use?: boolean Whether to disable parallel tool use. Defaults to false. If set to true, the model will output at most one tool use.
    • ToolChoiceAny The model will use any available tools.
      • type: "any"
        • "any"
      • disable_parallel_tool_use?: boolean Whether to disable parallel tool use. Defaults to false. If set to true, the model will output exactly one tool use.
    • ToolChoiceTool The model will use the specified tool with tool_choice.name.
      • name: string The name of the tool to use.
      • type: "tool"
        • "tool"
      • disable_parallel_tool_use?: boolean Whether to disable parallel tool use. Defaults to false. If set to true, the model will output exactly one tool use.
    • ToolChoiceNone The model will not be allowed to use tools.
      • type: "none"
        • "none"
  • tools?: Array<MessageCountTokensTool> Definitions of tools that the model may use. If you include tools in your API request, the model may return tool_use content blocks that represent the model’s use of those tools. You can then run those tools using the tool input generated by the model and then optionally return results back to the model using tool_result content blocks. There are two types of tools: client tools and server tools. The behavior described below applies to client tools. For server tools, see their individual documentation as each has its own behavior (e.g., the web search tool). Each tool definition includes:
    • name: Name of the tool.
    • description: Optional, but strongly-recommended description of the tool.
    • input_schema: JSON schema for the tool input shape that the model will produce in tool_use output content blocks.
    For example, if you defined tools as:
    [
      {
        "name": "get_stock_price",
        "description": "Get the current stock price for a given ticker symbol.",
        "input_schema": {
          "type": "object",
          "properties": {
            "ticker": {
              "type": "string",
              "description": "The stock ticker symbol, e.g. AAPL for Apple Inc."
            }
          },
          "required": ["ticker"]
        }
      }
    ]
    
    And then asked the model “What’s the S&P 500 at today?”, the model might produce tool_use content blocks in the response like this:
    [
      {
        "type": "tool_use",
        "id": "toolu_01D7FLrfh4GYq7yT1ULFeyMV",
        "name": "get_stock_price",
        "input": { "ticker": "^GSPC" }
      }
    ]
    
    You might then run your get_stock_price tool with {"ticker": "^GSPC"} as an input, and return the following back to the model in a subsequent user message:
    [
      {
        "type": "tool_result",
        "tool_use_id": "toolu_01D7FLrfh4GYq7yT1ULFeyMV",
        "content": "259.75 USD"
      }
    ]
    
    Tools can be used for workflows that include running client-side tools and functions, or more generally whenever you want the model to produce a particular JSON structure of output. See our guide for more details.
    • Tool
      • input_schema: InputSchema JSON schema for this tool’s input. This defines the shape of the input that your tool accepts and that the model will produce.
        • type: "object"
          • "object"
        • properties?: Record<string, unknown> | null
        • required?: Array<string> | null
      • name: string Name of the tool. This is how the tool will be called by the model and in tool_use blocks.
      • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
        • type: "ephemeral"
          • "ephemeral"
        • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
          • 5m: 5 minutes
          • 1h: 1 hour
          Defaults to 5m.
          • "5m"
          • "1h"
      • description?: string Description of what this tool does. Tool descriptions should be as detailed as possible. The more information that the model has about what the tool is and how to use it, the better it will perform. You can use natural language descriptions to reinforce important aspects of the tool input JSON schema.
      • type?: "custom" | null
        • "custom"
    • ToolBash20250124
      • name: "bash" Name of the tool. This is how the tool will be called by the model and in tool_use blocks.
        • "bash"
      • type: "bash_20250124"
        • "bash_20250124"
      • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
        • type: "ephemeral"
          • "ephemeral"
        • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
          • 5m: 5 minutes
          • 1h: 1 hour
          Defaults to 5m.
          • "5m"
          • "1h"
    • ToolTextEditor20250124
      • name: "str_replace_editor" Name of the tool. This is how the tool will be called by the model and in tool_use blocks.
        • "str_replace_editor"
      • type: "text_editor_20250124"
        • "text_editor_20250124"
      • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
        • type: "ephemeral"
          • "ephemeral"
        • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
          • 5m: 5 minutes
          • 1h: 1 hour
          Defaults to 5m.
          • "5m"
          • "1h"
    • ToolTextEditor20250429
      • name: "str_replace_based_edit_tool" Name of the tool. This is how the tool will be called by the model and in tool_use blocks.
        • "str_replace_based_edit_tool"
      • type: "text_editor_20250429"
        • "text_editor_20250429"
      • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
        • type: "ephemeral"
          • "ephemeral"
        • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
          • 5m: 5 minutes
          • 1h: 1 hour
          Defaults to 5m.
          • "5m"
          • "1h"
    • ToolTextEditor20250728
      • name: "str_replace_based_edit_tool" Name of the tool. This is how the tool will be called by the model and in tool_use blocks.
        • "str_replace_based_edit_tool"
      • type: "text_editor_20250728"
        • "text_editor_20250728"
      • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
        • type: "ephemeral"
          • "ephemeral"
        • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
          • 5m: 5 minutes
          • 1h: 1 hour
          Defaults to 5m.
          • "5m"
          • "1h"
      • max_characters?: number | null Maximum number of characters to display when viewing a file. If not specified, defaults to displaying the full file.
    • WebSearchTool20250305
      • name: "web_search" Name of the tool. This is how the tool will be called by the model and in tool_use blocks.
        • "web_search"
      • type: "web_search_20250305"
        • "web_search_20250305"
      • allowed_domains?: Array<string> | null If provided, only these domains will be included in results. Cannot be used alongside blocked_domains.
      • blocked_domains?: Array<string> | null If provided, these domains will never appear in results. Cannot be used alongside allowed_domains.
      • cache_control?: CacheControlEphemeral | null Create a cache control breakpoint at this content block.
        • type: "ephemeral"
          • "ephemeral"
        • ttl?: "5m" | "1h" The time-to-live for the cache control breakpoint. This may be one the following values:
          • 5m: 5 minutes
          • 1h: 1 hour
          Defaults to 5m.
          • "5m"
          • "1h"
      • max_uses?: number | null Maximum number of times the tool can be used in the API request.
      • user_location?: UserLocation | null Parameters for the user’s location. Used to provide more relevant search results.
        • type: "approximate"
          • "approximate"
        • city?: string | null The city of the user.
        • country?: string | null The two letter ISO country code of the user.
        • region?: string | null The region of the user.
        • timezone?: string | null The IANA timezone of the user.

​

Returns

• MessageTokensCount
  • input_tokens: number The total number of tokens across the provided list of messages, system prompt, and tools.

​

Example

import Anthropic from '@anthropic-ai/sdk';

const client = new Anthropic({
  apiKey: process.env['ANTHROPIC_API_KEY'], // This is the default and can be omitted
});

const messageTokensCount = await client.messages.countTokens({
  messages: [{ content: 'string', role: 'user' }],
  model: 'claude-opus-4-5-20251101',
});

console.log(messageTokensCount.input_tokens);