> ## Documentation Index > Fetch the complete documentation index at: https://docs.myrouter.ai/llms.txt > Use this file to discover all available pages before exploring further. # Create Anthropic-compatible message > Anthropic-compatible Messages invocation. Authorization Bearer is recommended; x-api-key is accepted only for SDK compatibility. ## OpenAPI ````yaml /openapi/v0-api/public.openapi.yaml post /anthropic/v1/messages openapi: 3.1.0 info: title: MyRouter V0 Public API version: 0.1.0 description: >- Customer-facing MyRouter V0 API. Core paths follow OpenRouter where possible; billing is a MyRouter extension using Stripe-style resource naming. license: name: Proprietary identifier: LicenseRef-Proprietary x-platform-contract-commit: 56b047ef2c076be151e090aa4e2f5e974180ea14 x-phase-sources: - phase1/2026-05-28-source-inventory.md - phase8/2026-05-28-public-v0-api-review-matrix.md servers: - url: https://api.myrouter.example description: Placeholder until public environment is finalized. security: - bearerApiKey: [] paths: /anthropic/v1/messages: post: tags: - Runtime summary: Create Anthropic-compatible message description: >- Anthropic-compatible Messages invocation. Authorization Bearer is recommended; x-api-key is accepted only for SDK compatibility. operationId: createAnthropicMessage parameters: - $ref: '#/components/parameters/RequestIdHeader' - name: anthropic-version in: header required: true schema: type: string description: Anthropic API version. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. - name: x-api-key in: header required: false schema: type: string description: >- Anthropic SDK-compatible API key header. Prefer Authorization: Bearer for MyRouter. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/AnthropicMessageRequest' responses: '200': description: Create Anthropic-compatible message response. headers: x-request-id: $ref: '#/components/headers/RequestId' content: application/json: schema: $ref: '#/components/schemas/AnthropicMessageResponse' '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/Unauthorized' '403': $ref: '#/components/responses/Forbidden' '404': $ref: '#/components/responses/NotFound' '429': $ref: '#/components/responses/RateLimited' '500': $ref: '#/components/responses/InternalError' components: parameters: RequestIdHeader: name: x-request-id in: header required: false schema: type: string description: Optional caller request id. x-source: Platform error contracts and product API convention x-owner: shared x-status: product-to-build x-platform-dependency: Platform runtime errors and product API errors x-rationale: Every API needs a stable supportable error envelope with request id. schemas: AnthropicMessageRequest: type: object additionalProperties: true required: - model - messages - max_tokens properties: model: type: string description: Public MyRouter model id exposed through Anthropic-compatible API. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. messages: type: array items: $ref: '#/components/schemas/AnthropicInputMessage' description: Anthropic-style input messages. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. minItems: 1 max_tokens: type: integer description: Maximum output tokens. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. minimum: 1 stream: type: boolean description: Whether to stream SSE events. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. system: oneOf: - type: string - type: array items: type: object additionalProperties: true description: System prompt content. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. stop_sequences: type: array items: type: string description: Stop sequences. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. temperature: type: number description: Sampling temperature. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. top_p: type: number description: Nucleus sampling value. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. top_k: type: integer description: Top-k sampling value. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. tools: type: array items: type: object additionalProperties: true description: Anthropic tool definitions. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. tool_choice: oneOf: - type: string - type: object additionalProperties: true description: Tool choice. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. metadata: type: object description: Customer metadata. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. additionalProperties: true x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. AnthropicMessageResponse: type: object additionalProperties: false required: - id - type - role - content - model properties: id: type: string description: Message id. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. type: type: string description: Anthropic response type. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. role: type: string description: Assistant role. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. content: type: array items: type: object additionalProperties: true description: Output content blocks. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. model: type: string description: Public MyRouter model id. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. stop_reason: type: string description: Why generation stopped. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. usage: $ref: '#/components/schemas/TokenUsage' description: Runtime usage facts, not invoice-grade charge evidence. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. AnthropicInputMessage: type: object additionalProperties: false required: - role - content properties: role: type: string description: Anthropic message role. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. enum: - user - assistant content: oneOf: - type: string - type: array items: type: object additionalProperties: true description: Message content. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. x-source: >- Anthropic Messages API plus platform Anthropic-compatible invocation@56b047e x-owner: platform x-status: current-platform-supported x-platform-dependency: Platform Anthropic-compatible messages x-rationale: >- Anthropic namespace is a compatibility extension; product recommends Authorization Bearer and documents x-api-key only for SDK compatibility. TokenUsage: type: object additionalProperties: false required: [] properties: input_tokens: type: integer description: Input token count when available. x-source: >- OpenAI/Anthropic usage report pattern plus June 4 platform usage aggregation x-owner: shared x-status: june-4-dependent x-platform-dependency: >- Platform usage aggregation by API key/account with 5-minute granularity x-rationale: >- Usage reports expose physical meters only, not customer charge amounts. minimum: 0 output_tokens: type: integer description: Output token count when available. x-source: >- OpenAI/Anthropic usage report pattern plus June 4 platform usage aggregation x-owner: shared x-status: june-4-dependent x-platform-dependency: >- Platform usage aggregation by API key/account with 5-minute granularity x-rationale: >- Usage reports expose physical meters only, not customer charge amounts. minimum: 0 total_tokens: type: integer description: Total token count when available. x-source: >- OpenAI/Anthropic usage report pattern plus June 4 platform usage aggregation x-owner: shared x-status: june-4-dependent x-platform-dependency: >- Platform usage aggregation by API key/account with 5-minute granularity x-rationale: >- Usage reports expose physical meters only, not customer charge amounts. minimum: 0 cache_read_tokens: type: integer description: Cache-read token count when available. x-source: >- OpenAI/Anthropic usage report pattern plus June 4 platform usage aggregation x-owner: shared x-status: june-4-dependent x-platform-dependency: >- Platform usage aggregation by API key/account with 5-minute granularity x-rationale: >- Usage reports expose physical meters only, not customer charge amounts. minimum: 0 cache_write_tokens: type: integer description: Cache-write token count when available. x-source: >- OpenAI/Anthropic usage report pattern plus June 4 platform usage aggregation x-owner: shared x-status: june-4-dependent x-platform-dependency: >- Platform usage aggregation by API key/account with 5-minute granularity x-rationale: >- Usage reports expose physical meters only, not customer charge amounts. minimum: 0 reasoning_tokens: type: integer description: Reasoning token count when available. x-source: >- OpenAI/Anthropic usage report pattern plus June 4 platform usage aggregation x-owner: shared x-status: june-4-dependent x-platform-dependency: >- Platform usage aggregation by API key/account with 5-minute granularity x-rationale: >- Usage reports expose physical meters only, not customer charge amounts. minimum: 0 x-source: >- OpenAI/Anthropic usage report pattern plus June 4 platform usage aggregation x-owner: shared x-status: june-4-dependent x-platform-dependency: Platform usage aggregation by API key/account with 5-minute granularity x-rationale: Usage reports expose physical meters only, not customer charge amounts. ErrorEnvelope: type: object additionalProperties: false required: - error - request_id properties: error: type: object additionalProperties: false required: - code - message properties: code: type: string description: Stable machine-readable error code. x-source: Platform error contracts and product API convention x-owner: shared x-status: product-to-build x-platform-dependency: Platform runtime errors and product API errors x-rationale: >- Every API needs a stable supportable error envelope with request id. message: type: string description: Human-readable error message. x-source: Platform error contracts and product API convention x-owner: shared x-status: product-to-build x-platform-dependency: Platform runtime errors and product API errors x-rationale: >- Every API needs a stable supportable error envelope with request id. type: type: string description: Error category. x-source: Platform error contracts and product API convention x-owner: shared x-status: product-to-build x-platform-dependency: Platform runtime errors and product API errors x-rationale: >- Every API needs a stable supportable error envelope with request id. x-source: Platform error contracts and product API convention x-owner: shared x-status: product-to-build x-platform-dependency: Platform runtime errors and product API errors x-rationale: Every API needs a stable supportable error envelope with request id. request_id: type: string description: Effective request id for support. x-source: Platform error contracts and product API convention x-owner: shared x-status: product-to-build x-platform-dependency: Platform runtime errors and product API errors x-rationale: Every API needs a stable supportable error envelope with request id. x-source: Platform error contracts and product API convention x-owner: shared x-status: product-to-build x-platform-dependency: Platform runtime errors and product API errors x-rationale: Every API needs a stable supportable error envelope with request id. headers: RequestId: schema: type: string description: Effective request id. x-source: Platform error contracts and product API convention x-owner: shared x-status: product-to-build x-platform-dependency: Platform runtime errors and product API errors x-rationale: Every API needs a stable supportable error envelope with request id. responses: BadRequest: description: Invalid request. content: application/json: schema: $ref: '#/components/schemas/ErrorEnvelope' Unauthorized: description: Missing or invalid authentication. content: application/json: schema: $ref: '#/components/schemas/ErrorEnvelope' Forbidden: description: Authenticated principal is not allowed. content: application/json: schema: $ref: '#/components/schemas/ErrorEnvelope' NotFound: description: Resource not found. content: application/json: schema: $ref: '#/components/schemas/ErrorEnvelope' RateLimited: description: Rate limit exceeded. content: application/json: schema: $ref: '#/components/schemas/ErrorEnvelope' InternalError: description: Internal error. content: application/json: schema: $ref: '#/components/schemas/ErrorEnvelope' securitySchemes: bearerApiKey: type: http scheme: bearer bearerFormat: MyRouter API key ````