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## Claude API versus cloud platforms ## Claude API vs cloud platforms
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2323
2424The Claude API includes the following APIs:
2525
26* **[Messages API](https://platform.claude.com/docs/en/api/messages/create)**: Send messages to Claude for conversational interactions (`POST /v1/messages`)
27* **[Message Batches API](https://platform.claude.com/docs/en/api/messages/batches/create)**: Process large volumes of Messages requests asynchronously with 50% cost reduction (`POST /v1/messages/batches`)
28* **[Token Counting API](https://platform.claude.com/docs/en/api/messages/count_tokens)**: Count tokens in a message before sending to manage costs and rate limits (`POST /v1/messages/count_tokens`)
29* **[Models API](https://platform.claude.com/docs/en/api/models/list)**: List available Claude models and their details (`GET /v1/models`)
30* **[Files API](https://platform.claude.com/docs/en/api/files/upload)**: Upload and manage files for use across multiple API calls (`POST /v1/files`, `GET /v1/files`)
31* **[Skills API](https://platform.claude.com/docs/en/api/skills/create)**: Create and manage custom agent skills (`POST /v1/skills`, `GET /v1/skills`)
26* **[Messages API](https://platform.claude.com/docs/en/api/messages/create):** Send messages to Claude for conversational interactions (`POST /v1/messages`)
27* **[Message Batches API](https://platform.claude.com/docs/en/api/messages/batches/create):** Process large volumes of Messages requests asynchronously with a 50 percent cost reduction (`POST /v1/messages/batches`)
28* **[Token Counting API](https://platform.claude.com/docs/en/api/messages/count_tokens):** Count tokens in a message before sending to manage costs and rate limits (`POST /v1/messages/count_tokens`)
29* **[Models API](https://platform.claude.com/docs/en/api/models/list):** List available Claude models and their details (`GET /v1/models`)
30* **[Files API](https://platform.claude.com/docs/en/api/files/upload):** Upload and manage files for use across multiple API calls (`POST /v1/files`, `GET /v1/files`)
31* **[Skills API](https://platform.claude.com/docs/en/api/skills/create):** Create and manage custom agent skills (`POST /v1/skills`, `GET /v1/skills`)
3232
3333The following APIs are in beta:
3434
35* **[Agents API](https://platform.claude.com/docs/en/managed-agents/agent-setup)**: Define reusable, versioned agent configurations for Claude Managed Agents (`POST /v1/agents`, `GET /v1/agents`)
36* **[Sessions API](https://platform.claude.com/docs/en/managed-agents/sessions)**: Run stateful agent sessions in managed cloud sandboxes (`POST /v1/sessions`, `GET /v1/sessions/{id}/events/stream`)
37* **[Environments API](https://platform.claude.com/docs/en/managed-agents/environments)**: Configure sandbox templates for agent sessions (`POST /v1/environments`, `GET /v1/environments`)
35* **[Agents API](https://platform.claude.com/docs/en/managed-agents/agent-setup):** Define reusable, versioned agent configurations for Claude Managed Agents (`POST /v1/agents`, `GET /v1/agents`)
36* **[Sessions API](https://platform.claude.com/docs/en/managed-agents/sessions):** Run stateful agent sessions in managed cloud sandboxes (`POST /v1/sessions`, `GET /v1/sessions/{id}/events/stream`)
37* **[Environments API](https://platform.claude.com/docs/en/managed-agents/environments):** Configure sandbox templates for agent sessions (`POST /v1/environments`, `GET /v1/environments`)
3838
3939For 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](https://platform.claude.com/docs/en/api/beta-headers).
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4242
4343For details on each authentication method and when to use it, see [Authentication](https://platform.claude.com/docs/en/manage-claude/authentication). Requests to the Claude API include these headers:
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45| Header | Value | Required |
46| ------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
47| `Authorization` | `Bearer <token>`, where `<token>` is your API key or a short-lived access token obtained from `POST /v1/oauth/token` through [Workload Identity Federation](https://platform.claude.com/docs/en/manage-claude/workload-identity-federation) | Yes, unless `x-api-key` is set |
48| `x-api-key` | Your API key from Console. Legacy fallback for `Authorization`, still supported | No |
49| `anthropic-workspace-id` | ID of the [workspace](https://platform.claude.com/docs/en/manage-claude/workspaces) the request runs in (for example, `wrkspc_01JwQvzr7rXLA5AGx3HKfFUJ`). See [Select a workspace](https://platform.claude.com/docs/en/manage-claude/authentication#select-a-workspace). | Required with a multi-workspace API key. Optional for other API keys. A key created for a single workspace runs in that workspace when you omit the header. Not used with Workload Identity Federation tokens, which select a workspace at token exchange. |
50| `anthropic-version` | API version (for example, `2026-10-21`) | Yes |
51| `content-type` | `application/json` | Yes |
45| Header | Value | Required |
46| ------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
47| `Authorization` | `Bearer <token>`, where `<token>` is your API key or a short-lived access token obtained from `POST /v1/oauth/token` through [Workload Identity Federation](https://platform.claude.com/docs/en/manage-claude/workload-identity-federation) | Yes, unless `x-api-key` is set |
48| `x-api-key` | Your API key from Console. Legacy fallback for `Authorization`, still supported | No |
49| `anthropic-workspace-id` | ID of the [workspace](https://platform.claude.com/docs/en/manage-claude/workspaces) the request runs in (for example, `wrkspc_01JwQvzr7rXLA5AGx3HKfFUJ`). See [Select a workspace](https://platform.claude.com/docs/en/manage-claude/authentication#select-a-workspace). | Required with an API key that isn't scoped to a workspace. Optional for other API keys. A key created for a single workspace runs in that workspace when you omit the header. Not used with Workload Identity Federation tokens, which select a workspace at token exchange. |
50| `anthropic-version` | API version (for example, `2026-10-21`) | Yes |
51| `content-type` | `application/json` | Yes |
5252
5353If you are using the [Client SDKs](https://platform.claude.com/docs/en/api/overview#client-sdks), the SDK sends the authentication, version, and content-type headers automatically; you pass `anthropic-workspace-id` yourself when your key needs it. For API versioning details, see [API versions](https://platform.claude.com/docs/en/api/versioning).
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7070* Streaming support
7171* Request timeouts and connection management
7272
73For a list of client SDKs, see [Client SDKs](https://platform.claude.com/docs/en/cli-sdks-libraries/overview).
73For a list of client SDKs, see [SDKs, CLI, and libraries](https://platform.claude.com/docs/en/cli-sdks-libraries/overview).
7474
75## Claude API vs cloud platforms
75## Claude API versus cloud platforms
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7777Claude is available through the direct Claude API and through cloud platforms. Choose based on your infrastructure, feature availability, compliance requirements, and pricing preferences.
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105105
106106### Request size limits
107107
108| Endpoint | Maximum request size |
109| --------------------------------------------------------------------------------------------- | -------------------- |
110| Messages, Token Counting | 32 MB |
111| [Message Batches API](https://platform.claude.com/docs/en/build-with-claude/batch-processing) | 256 MB |
112| [Files API](https://platform.claude.com/docs/en/build-with-claude/files) | 500 MB |
113| Sessions, Agents, Environments | 32 MB |
108| Endpoint | Maximum request size |
109| -------------------------------------------------------------------------------------------------------------------- | -------------------- |
110| Messages, Token Counting | 32 MB |
111| Message Batches API (see [Batch processing](https://platform.claude.com/docs/en/build-with-claude/batch-processing)) | 256 MB |
112| [Files API](https://platform.claude.com/docs/en/build-with-claude/files) | 500 MB |
113| Sessions, Agents, Environments | 32 MB |
114114
115115If you exceed these limits, you'll receive a 413 `request_too_large` error.
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148148
149149To go back a page, pass `prev_page` as the `page` parameter. `prev_page` is `null` when you're on the first page. Not all list endpoints support `prev_page`. Only `GET /v1/sessions` returns `prev_page`; on list endpoints that do not support backward pagination, the field is absent from the response rather than `null`. For a request walkthrough, see [Listing sessions](https://platform.claude.com/docs/en/managed-agents/session-operations#listing-sessions).
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151The SDK provides an auto-paginating iterator that follows `next_page` for you. For example, `for session in client.beta.sessions.list()` (typescript: `for await (const session of client.beta.sessions.list())`; go: `client.Beta.Sessions.ListAutoPaging()`; java: `client.beta().sessions().list().autoPager()`; csharp: `(await client.Beta.Sessions.List()).Paginate()`; php: `$client->beta->sessions->list()->pagingEachItem()`; ruby: `client.beta.sessions.list.auto_paging_each`) walks through every session. SDK auto-pagination is forward-only; to go back a page, read `prev_page` from the response and pass it back as the `page` parameter yourself. See [client SDKs](https://platform.claude.com/docs/en/cli-sdks-libraries/overview) for details.
151The SDK provides an auto-paginating iterator that follows `next_page` for you. For example, `for session in client.beta.sessions.list()` (typescript: `for await (const session of client.beta.sessions.list())`; go: `client.Beta.Sessions.ListAutoPaging()`; java: `client.beta().sessions().list().autoPager()`; csharp: `(await client.Beta.Sessions.List()).Paginate()`; php: `$client->beta->sessions->list()->pagingEachItem()`; ruby: `client.beta.sessions.list.auto_paging_each`) walks through every session. SDK auto-pagination is forward-only; to go back a page, read `prev_page` from the response and pass it back as the `page` parameter yourself. See [SDKs, CLI, and libraries](https://platform.claude.com/docs/en/cli-sdks-libraries/overview) for details.
152152
153153<Note>
154 Some list endpoints use a different cursor scheme. The [Message Batches API](https://platform.claude.com/docs/en/build-with-claude/batch-processing), the [Models API](https://platform.claude.com/docs/en/api/models/list), and several [Admin API](https://platform.claude.com/docs/en/manage-claude/admin-api) endpoints take `after_id` and `before_id` query parameters instead of `page`. Their responses return `has_more`, `first_id`, and `last_id` instead of `next_page`. See the reference page for each endpoint for its exact pagination fields.
154 Some list endpoints use a different cursor scheme. The Message Batches API (see [Batch processing](https://platform.claude.com/docs/en/build-with-claude/batch-processing)), the [Models API](https://platform.claude.com/docs/en/api/models/list), and several [Admin API](https://platform.claude.com/docs/en/manage-claude/admin-api) endpoints take `after_id` and `before_id` query parameters instead of `page`. Their responses return `has_more`, `first_id`, and `last_id` instead of `next_page`. See the reference page for each endpoint for its exact pagination fields.
155155</Note>
156156
157157## Rate limits and availability
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161161The API enforces rate limits and spend limits to prevent misuse and manage capacity. Limits are organized into usage tiers; your organization is placed on a tier automatically and can move to a higher tier over time. Each tier has:
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163* **Spend limits**: Maximum monthly cost for API usage
164* **Rate limits**: Maximum number of requests per minute (RPM) and tokens per minute (TPM)
163* **Spend limits:** Maximum monthly cost for API usage
164* **Rate limits:** Maximum number of requests per minute (RPM) and tokens per minute (TPM)
165165
166In the Console, you can view your rate limits on the [Rate limits](https://platform.claude.com/usage/limits) page and your spend limits on the [Billing](https://platform.claude.com/settings/billing) page. For higher rate limits or a higher monthly spend cap, use **Request tier increase** on the Rate limits page.
166In the Console, you can view your rate limits on the [Rate limits](https://platform.claude.com/usage/limits) page and your spend limits on the [Billing](https://platform.claude.com/settings/billing) page. For higher rate limits or a higher monthly spend cap, use **Request tier increase** on the **Rate limits** page.
167167
168168For detailed information about limits, tiers, and the token bucket algorithm used for rate limiting, see [Rate limits](https://platform.claude.com/docs/en/api/rate-limits).
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