> ## Documentation Index > Fetch the complete documentation index at: https://docs.cfosilvia.com/llms.txt > Use this file to discover all available pages before exploring further. # Api overview # API Overview *** The Claude API is a RESTful API at `https://api.anthropic.com` that provides programmatic access to Claude models. The primary API is the Messages API (`POST /v1/messages`) for conversational interactions. **New to Claude?** Start with [Get started](/docs/en/get-started) for prerequisites and your first API call, or see [Working with Messages](/docs/en/build-with-claude/working-with-messages) for request/response patterns and examples. ## Prerequisites To use the Claude API, you'll need: * An [Anthropic Console account](https://console.anthropic.com) * An [API key](/settings/keys) For step-by-step setup instructions, see [Get started](/docs/en/get-started). ## Available APIs The Claude API includes the following APIs: **General Availability:** * **[Messages API](/docs/en/api/messages)**: Send messages to Claude for conversational interactions (`POST /v1/messages`) * **[Message Batches API](/docs/en/api/creating-message-batches)**: Process large volumes of Messages requests asynchronously with 50% cost reduction (`POST /v1/messages/batches`) * **[Token Counting API](/docs/en/api/messages-count-tokens)**: Count tokens in a message before sending to manage costs and rate limits (`POST /v1/messages/count_tokens`) * **[Models API](/docs/en/api/models-list)**: List available Claude models and their details (`GET /v1/models`) **Beta:** * **[Files API](/docs/en/api/files-create)**: Upload and manage files for use across multiple API calls (`POST /v1/files`, `GET /v1/files`) * **[Skills API](/docs/en/api/skills/create-skill)**: Create and manage custom agent skills (`POST /v1/skills`, `GET /v1/skills`) For the complete API reference with all endpoints, parameters, and response schemas, explore the API reference pages listed in the navigation. To access beta features, see [Beta headers](/docs/en/api/beta-headers). ## Authentication All requests to the Claude API must include these headers: | Header | Value | Required | | - | - | - | | `x-api-key` | Your API key from Console | Yes | | `anthropic-version` | API version (e.g., `2023-06-01`) | Yes | | `content-type` | `application/json` | Yes | If you are using the [Client SDKs](#client-sdks), the SDK will send these headers automatically. For API versioning details, see [API versions](/docs/en/api/versioning). ### Getting API Keys The API is made available via the web [Console](https://console.anthropic.com/). You can use the [Workbench](https://console.anthropic.com/workbench) to try out the API in the browser and then generate API keys in [Account Settings](https://console.anthropic.com/settings/keys). Use [workspaces](https://console.anthropic.com/settings/workspaces) to segment your API keys and [control spend](/docs/en/api/rate-limits) by use case. ## Client SDKs Anthropic provides official SDKs that simplify API integration by handling authentication, request formatting, error handling, and more. **Benefits**: * Automatic header management (x-api-key, anthropic-version, content-type) * Type-safe request and response handling * Built-in retry logic and error handling * Streaming support * Request timeouts and connection management **Example** (Python): ```python theme={null} from anthropic import Anthropic client = Anthropic() # Reads ANTHROPIC_API_KEY from environment message = client.messages.create( model="claude-sonnet-4-5", max_tokens=1024, messages=[{"role": "user", "content": "Hello, Claude"}] ) ``` For a list of client SDKs and their respective installation instructions, see [Client SDKs](/docs/en/api/client-sdks). ## Claude API vs Third-Party Platforms Claude is available through Anthropic's direct API and through partner platforms. Choose based on your infrastructure, compliance requirements, and pricing preferences. ### Claude API * **Direct access** to the latest models and features first * **Anthropic billing and support** * **Best for**: New integrations, full feature access, direct relationship with Anthropic ### Third-Party Platform APIs Access Claude through AWS, Google Cloud, or Microsoft Azure: * **Integrated** with cloud provider billing and IAM * **May have feature delays** or differences from the direct API * **Best for**: Existing cloud commitments, specific compliance requirements, consolidated cloud billing | Platform | Provider | Documentation | | - | - | - | | Amazon Bedrock | AWS | [Claude on Amazon Bedrock](/docs/en/build-with-claude/claude-on-amazon-bedrock) | | Vertex AI | Google Cloud | [Claude on Vertex AI](/docs/en/build-with-claude/claude-on-vertex-ai) | | Azure AI | Microsoft Azure | [Claude on Azure AI](/docs/en/build-with-claude/claude-in-microsoft-foundry) | For feature availability across platforms, see the [Features overview](/docs/en/build-with-claude/overview). ## Request and Response Format ### Request Size Limits The API has different maximum request sizes depending on the endpoint: | Endpoint | Maximum Size | | - | - | | Standard endpoints (Messages, Token Counting) | 32 MB | | [Batch API](/docs/en/build-with-claude/batch-processing) | 256 MB | | [Files API](/docs/en/build-with-claude/files) | 500 MB | If you exceed these limits, you'll receive a 413 `request_too_large` error. ### Response Headers The Claude API includes the following headers in every response: * `request-id`: A globally unique identifier for the request * `anthropic-organization-id`: The organization ID associated with the API key used in the request ## Rate Limits and Availability ### Rate Limits The API enforces rate limits and spend limits to prevent misuse and manage capacity. Limits are organized into usage tiers that increase automatically as you use the API. Each tier has: * **Spend limits**: Maximum monthly cost for API usage * **Rate limits**: Maximum number of requests per minute (RPM) and tokens per minute (TPM) You can view your organization's current limits in the [Console](/settings/limits). For higher limits or Priority Tier (enhanced service levels with committed spend), contact sales through the Console. For detailed information about limits, tiers, and the token bucket algorithm used for rate limiting, see [Rate limits](/docs/en/api/rate-limits). ### Availability The Claude API is available in [many countries and regions](/docs/en/api/supported-regions) worldwide. Check the supported regions page to confirm availability in your location. ## Basic Example Here's a minimal request using the Messages API: ```bash theme={null} curl https://api.anthropic.com/v1/messages \ --header "x-api-key: $ANTHROPIC_API_KEY" \ --header "anthropic-version: 2023-06-01" \ --header "content-type: application/json" \ --data '{ "model": "claude-sonnet-4-5", "max_tokens": 1024, "messages": [ {"role": "user", "content": "Hello, Claude"} ] }' ``` **Response:** ```json theme={null} { "id": "msg_01XFDUDYJgAACzvnptvVoYEL", "type": "message", "role": "assistant", "content": [ { "type": "text", "text": "Hello! How can I assist you today?" } ], "model": "claude-sonnet-4-5", "stop_reason": "end_turn", "usage": { "input_tokens": 12, "output_tokens": 8 } } ``` For complete examples and tutorials, see [Get started](/docs/en/get-started) and [Working with Messages](/docs/en/build-with-claude/working-with-messages). ## Next Steps Prerequisites, step-by-step tutorial, and examples in multiple languages Request/response patterns, multi-turn conversations, and best practices Complete API specification: parameters, responses, and error codes Installation guides for Python, TypeScript, Java, Go, C#, Ruby, and PHP Explore capabilities: caching, vision, tool use, streaming, and more Usage tiers, spend limits, and rate limiting with token bucket algorithm # Client SDKs We provide client libraries in a number of popular languages that make it easier to work with the Claude API. *** This page includes brief installation instructions and links to the open-source GitHub repositories for Anthropic's Client SDKs. For basic usage instructions, see the [API reference](/docs/en/api/overview) For detailed usage instructions, refer to each SDK's GitHub repository. Additional configuration is needed to use Anthropic's Client SDKs through a partner platform. If you are using Amazon Bedrock, see [this guide](/docs/en/build-with-claude/claude-on-amazon-bedrock); if you are using Google Cloud Vertex AI, see [this guide](/docs/en/build-with-claude/claude-on-vertex-ai); if you are using Microsoft Foundry, see [this guide](/docs/en/build-with-claude/claude-in-microsoft-foundry). ## Python [Python library GitHub repo](https://github.com/anthropics/anthropic-sdk-python) **Requirements:** Python 3.8+ **Installation:** ```bash theme={null} pip install anthropic ``` *** ## TypeScript [TypeScript library GitHub repo](https://github.com/anthropics/anthropic-sdk-typescript) While this library is in TypeScript, it can also be used in JavaScript libraries. **Installation:** ```bash theme={null} npm install @anthropic-ai/sdk ``` *** ## Java [Java library GitHub repo](https://github.com/anthropics/anthropic-sdk-java) **Requirements:** Java 8 or later **Installation:** Gradle: ```groovy theme={null} implementation("com.anthropic:anthropic-java:2.10.0") ``` Maven: ```xml theme={null} com.anthropic anthropic-java 2.10.0 ``` *** ## Go [Go library GitHub repo](https://github.com/anthropics/anthropic-sdk-go) **Requirements:** Go 1.22+ **Installation:** ```bash theme={null} go get -u 'github.com/anthropics/anthropic-sdk-go@v1.17.0' ``` *** ## C\# [C# library GitHub repo](https://github.com/anthropics/anthropic-sdk-csharp) The C# SDK is currently in beta. **Requirements:** .NET 8 or later **Installation:** ```bash theme={null} dotnet add package Anthropic ``` *** ## Ruby [Ruby library GitHub repo](https://github.com/anthropics/anthropic-sdk-ruby) **Requirements:** Ruby 3.2.0 or later **Installation:** Add to your Gemfile: ```ruby theme={null} gem "anthropic", "~> 1.13.0" ``` Then run: ```bash theme={null} bundle install ``` *** ## PHP [PHP library GitHub repo](https://github.com/anthropics/anthropic-sdk-php) The PHP SDK is currently in beta. **Requirements:** PHP 8.1.0 or higher **Installation:** ```bash theme={null} composer require "anthropic-ai/sdk 0.3.0" ``` *** ## Beta namespace in client SDKs Every SDK has a `beta` namespace that is available for accessing new features that Anthropic releases in beta versions. Use this in conjunction with [beta headers](/docs/en/api/beta-headers) to access these features. Refer to each SDK's GitHub repository for specific usage examples. # Beta headers Documentation for using beta headers with the Claude API *** Beta headers allow you to access experimental features and new model capabilities before they become part of the standard API. These features are subject to change and may be modified or removed in future releases. Beta headers are often used in conjunction with the [beta namespace in the client SDKs](/docs/en/api/client-sdks#beta-namespace-in-client-sdks) ## How to use beta headers To access beta features, include the `anthropic-beta` header in your API requests: ```http theme={null} POST /v1/messages Content-Type: application/json X-API-Key: YOUR_API_KEY anthropic-beta: BETA_FEATURE_NAME ``` When using the SDK, you can specify beta headers in the request options: ```python Python theme={null} from anthropic import Anthropic client = Anthropic() response = client.beta.messages.create( model="claude-sonnet-4-5", max_tokens=1024, messages=[ {"role": "user", "content": "Hello, Claude"} ], betas=["beta-feature-name"] ) ``` ```typescript TypeScript theme={null} import Anthropic from '@anthropic-ai/sdk'; const anthropic = new Anthropic(); const msg = await anthropic.beta.messages.create({ model: 'claude-sonnet-4-5', max_tokens: 1024, messages: [ { role: 'user', content: 'Hello, Claude' } ], betas: ['beta-feature-name'] }); ``` ```bash cURL theme={null} curl https://api.anthropic.com/v1/messages \ -H "x-api-key: $ANTHROPIC_API_KEY" \ -H "anthropic-version: 2023-06-01" \ -H "anthropic-beta: beta-feature-name" \ -H "content-type: application/json" \ -d '{ "model": "claude-sonnet-4-5", "max_tokens": 1024, "messages": [ {"role": "user", "content": "Hello, Claude"} ] }' ``` Beta features are experimental and may: * Have breaking changes without notice * Be deprecated or removed * Have different rate limits or pricing * Not be available in all regions ### Multiple beta features To use multiple beta features in a single request, include all feature names in the header separated by commas: ```http theme={null} anthropic-beta: feature1,feature2,feature3 ``` ### Version naming conventions Beta feature names typically follow the pattern: `feature-name-YYYY-MM-DD`, where the date indicates when the beta version was released. Always use the exact beta feature name as documented. ## Error handling If you use an invalid or unavailable beta header, you'll receive an error response: ```json theme={null} { "type": "error", "error": { "type": "invalid_request_error", "message": "Unsupported beta header: invalid-beta-name" } } ``` ## Getting help For questions about beta features: 1. Check the documentation for the specific feature 2. Review the [API changelog](/docs/en/api/versioning) for updates 3. Contact support for assistance with production usage Remember that beta features are provided "as-is" and may not have the same SLA guarantees as stable API features. # Errors *** ## HTTP errors Our API follows a predictable HTTP error code format: * 400 - `invalid_request_error`: There was an issue with the format or content of your request. We may also use this error type for other 4XX status codes not listed below. * 401 - `authentication_error`: There's an issue with your API key. * 403 - `permission_error`: Your API key does not have permission to use the specified resource. * 404 - `not_found_error`: The requested resource was not found. * 413 - `request_too_large`: Request exceeds the maximum allowed number of bytes. The maximum request size is 32 MB for standard API endpoints. * 429 - `rate_limit_error`: Your account has hit a rate limit. * 500 - `api_error`: An unexpected error has occurred internal to Anthropic's systems. * 529 - `overloaded_error`: The API is temporarily overloaded. 529 errors can occur when APIs experience high traffic across all users. In rare cases, if your organization has a sharp increase in usage, you might see 429 errors due to acceleration limits on the API. To avoid hitting acceleration limits, ramp up your traffic gradually and maintain consistent usage patterns. When receiving a [streaming](/docs/en/build-with-claude/streaming) response via SSE, it's possible that an error can occur after returning a 200 response, in which case error handling wouldn't follow these standard mechanisms. ## Request size limits The API enforces request size limits to ensure optimal performance: | Endpoint Type | Maximum Request Size | | :- | :- | | Messages API | 32 MB | | Token Counting API | 32 MB | | [Batch API](/docs/en/build-with-claude/batch-processing) | 256 MB | | [Files API](/docs/en/build-with-claude/files) | 500 MB | If you exceed these limits, you'll receive a 413 `request_too_large` error. The error is returned from Cloudflare before the request reaches our API servers. ## Error shapes Errors are always returned as JSON, with a top-level `error` object that always includes a `type` and `message` value. The response also includes a `request_id` field for easier tracking and debugging. For example: ```json JSON theme={null} { "type": "error", "error": { "type": "not_found_error", "message": "The requested resource could not be found." }, "request_id": "req_011CSHoEeqs5C35K2UUqR7Fy" } ``` In accordance with our [versioning](/docs/en/api/versioning) policy, we may expand the values within these objects, and it is possible that the `type` values will grow over time. ## Request id Every API response includes a unique `request-id` header. This header contains a value such as `req_018EeWyXxfu5pfWkrYcMdjWG`. When contacting support about a specific request, please include this ID to help us quickly resolve your issue. Our official SDKs provide this value as a property on top-level response objects, containing the value of the `request-id` header: ```python Python theme={null} import anthropic client = anthropic.Anthropic() message = client.messages.create( model="claude-sonnet-4-5", max_tokens=1024, messages=[ {"role": "user", "content": "Hello, Claude"} ] ) print(f"Request ID: {message._request_id}") ``` ```typescript TypeScript theme={null} import Anthropic from '@anthropic-ai/sdk'; const client = new Anthropic(); const message = await client.messages.create({ model: 'claude-sonnet-4-5', max_tokens: 1024, messages: [ {"role": "user", "content": "Hello, Claude"} ] }); console.log('Request ID:', message._request_id); ``` ## Long requests We highly encourage using the [streaming Messages API](/docs/en/build-with-claude/streaming) or [Message Batches API](/docs/en/api/creating-message-batches) for long running requests, especially those over 10 minutes. We do not recommend setting a large `max_tokens` values without using our [streaming Messages API](/docs/en/build-with-claude/streaming) or [Message Batches API](/docs/en/api/creating-message-batches): * Some networks may drop idle connections after a variable period of time, which can cause the request to fail or timeout without receiving a response from Anthropic. * Networks differ in reliability; our [Message Batches API](/docs/en/api/creating-message-batches) can help you manage the risk of network issues by allowing you to poll for results rather than requiring an uninterrupted network connection. If you are building a direct API integration, you should be aware that setting a [TCP socket keep-alive](https://tldp.org/HOWTO/TCP-Keepalive-HOWTO/programming.html) can reduce the impact of idle connection timeouts on some networks. Our [SDKs](/docs/en/api/client-sdks) will validate that your non-streaming Messages API requests are not expected to exceed a 10 minute timeout and also will set a socket option for TCP keep-alive. This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.