> ## Documentation Index > Fetch the complete documentation index at: https://runcrate.ai/docs/llms.txt > Use this file to discover all available pages before exploring further. # Messages (Anthropic-compatible) > The Anthropic Messages API, so Claude Code and the Anthropic SDKs work with a Runcrate key and Runcrate model ids. Same billing, limits and models as chat completions. Errors use Anthropic's shape: `{type: error, error: {type, message, code}}`. ## OpenAPI ````yaml /api-reference/openapi.json post /messages openapi: 3.1.0 info: title: Runcrate API version: 1.0.0 summary: OpenAI-compatible inference API + GPU infrastructure API. description: >- Runcrate exposes two API surfaces. The inference API at `https://api.runcrate.ai/v1` is OpenAI-compatible: it accepts the standard OpenAI SDK with the base URL changed. The infrastructure API at `https://www.runcrate.ai/api/v1` manages GPU instances, jobs, persistent volumes, environments, SSH keys, templates, and billing. Both share a single `rc_live_*` API key. Pricing is per-token, per-image, per-second, or per-minute on the inference API (varies by model; see https://www.runcrate.ai/api/models/catalog for live rates) and per-second on GPU rentals (see https://www.runcrate.ai/pricing for hourly rates per GPU class). All infrastructure API responses are wrapped in `{ "data": ... }`. List responses also include a `meta` object with pagination cursors. Error responses use `{ "error": { "code": "...", "message": "..." } }`. termsOfService: https://www.runcrate.ai/terms contact: name: Runcrate url: https://www.runcrate.ai/contact license: name: Proprietary url: https://www.runcrate.ai/terms servers: - url: https://api.runcrate.ai/v1 description: Inference API (OpenAI-compatible) - url: https://www.runcrate.ai/api/v1 description: >- Infrastructure API (instances, jobs, storage, environments, ssh-keys, templates, billing) security: - ApiKeyAuth: [] tags: - name: Chat description: OpenAI-compatible chat completions. - name: Messages description: Anthropic-compatible Messages API, for Claude Code and the Anthropic SDKs. - name: Responses description: >- OpenAI-compatible Responses API, for Codex and responses.create. Nothing is stored. - name: Images description: Text-to-image generation. - name: Videos description: Async text-to-video and image-to-video generation. - name: Audio description: Text-to-speech and speech-to-text. - name: Embeddings description: Vector embeddings for RAG and search. - name: Models description: Model catalog discovery. - name: Instances description: GPU instance lifecycle. - name: Jobs description: >- Run one command on its own GPU machine. The machine stops, and billing ends, when the command exits. - name: Schedules description: >- Start an instance or a job later: once at a set time, or on a repeating cron schedule in your timezone. - name: Storage description: Persistent volume management. - name: Environments description: Resource isolation containers within a workspace. - name: Secrets description: >- Names of the secrets an environment's machines get. Values are set in the dashboard and never returned. - name: SSH Keys description: SSH key management for instance access. - name: Templates description: Pre-built instance images and configurations. - name: Billing description: Credit balance, transactions, usage metrics. paths: /messages: post: tags: - Messages summary: Messages (Anthropic-compatible) description: >- The Anthropic Messages API, so Claude Code and the Anthropic SDKs work with a Runcrate key and Runcrate model ids. Same billing, limits and models as chat completions. Errors use Anthropic's shape: `{type: error, error: {type, message, code}}`. operationId: createMessage requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/MessagesRequest' responses: '200': description: >- A message (or an SSE stream of message_start, content_block_start, content_block_delta, content_block_stop, message_delta, message_stop and ping events when stream=true). content: application/json: schema: $ref: '#/components/schemas/MessagesResponse' text/event-stream: schema: type: string description: Anthropic Messages stream events. '401': $ref: '#/components/responses/Unauthorized' '402': $ref: '#/components/responses/PaymentRequired' '404': description: >- Unknown model. A Claude model name (Claude Code's default when ANTHROPIC_MODEL is unset) is told to set ANTHROPIC_MODEL to a Runcrate model id. '429': $ref: '#/components/responses/RateLimited' security: - ApiKeyAuth: [] - AnthropicApiKey: [] components: schemas: MessagesRequest: type: object required: - model - messages properties: model: type: string description: >- A Runcrate model id (e.g. `deepseek-ai/DeepSeek-V4.1-Flash`). Claude model names such as `claude-sonnet-4-5` are not Runcrate ids and answer 404. messages: type: array description: >- Turns with `role` (`user` or `assistant`) and `content`: a string, or blocks of type `text`, `image` (base64 or url source), `document` (text source), `tool_use` and `tool_result` (with `is_error`). `thinking` blocks sent back are accepted and not passed to the model. items: type: object system: oneOf: - type: string - type: array items: type: object description: A string or text blocks; `cache_control` is kept. max_tokens: type: integer minimum: 1 temperature: type: number top_p: type: number top_k: type: integer stop_sequences: type: array items: type: string stream: type: boolean default: false tools: type: array description: Custom tools with `name`, `description` and `input_schema`. items: type: object tool_choice: type: object description: >- `{type: auto | any | tool | none}`; `tool` takes `name`; `disable_parallel_tool_use` is honored. thinking: type: object description: >- `{type: enabled, budget_tokens}` sets the reasoning effort: under 4,096 low, under 16,384 medium, else high. `output_config.effort` takes precedence. metadata: type: object description: Accepted and never sent to the model. MessagesResponse: type: object properties: id: type: string type: type: string enum: - message role: type: string enum: - assistant model: type: string content: type: array description: >- `thinking`, then `text`, then `tool_use` blocks (with parsed `input`). items: type: object stop_reason: type: string enum: - end_turn - max_tokens - stop_sequence - tool_use - refusal stop_sequence: type: string nullable: true usage: type: object properties: input_tokens: type: integer output_tokens: type: integer cache_read_input_tokens: type: integer cache_creation_input_tokens: type: integer Error: type: object required: - error properties: error: type: object required: - code - message properties: code: type: string description: >- Machine-readable error code (e.g. `validation_error`, `unauthorized`, `not_found`, `insufficient_credits`, `rate_limited`, `internal_error`). message: type: string description: Human-readable error message. details: type: object additionalProperties: true description: Optional structured error context. responses: Unauthorized: description: Missing or invalid API key. content: application/json: schema: $ref: '#/components/schemas/Error' PaymentRequired: description: >- Insufficient credits, the environment has reached its monthly budget (error code `BUDGET_REACHED`), or launches are paused while a payment on the workspace is disputed (`PAYMENT_HOLD`). content: application/json: schema: $ref: '#/components/schemas/Error' RateLimited: description: Rate limited. Retry with exponential backoff. content: application/json: schema: $ref: '#/components/schemas/Error' securitySchemes: ApiKeyAuth: type: http scheme: bearer description: >- Use a Runcrate API key with the `rc_live_*` prefix as the bearer token. Create one at https://www.runcrate.ai/dashboard/api-keys. AnthropicApiKey: type: apiKey in: header name: x-api-key description: >- The Messages API also takes the Runcrate key in `x-api-key`, as the Anthropic SDKs send it. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.