> ## Documentation Index > Fetch the complete documentation index at: https://docs.ninjachat.ai/llms.txt > Use this file to discover all available pages before exploring further. # Create an Anthropic-compatible message > Messages compatibility for text, image inputs, JSON output schemas, function tools and SSE. Accepts Authorization bearer or x-api-key. Uses the same metered gateway, routing and idempotency as Chat Completions. Native server tools, file IDs and signed thinking history are not supported; unsupported parameters return explicit errors. ## OpenAPI ````yaml /openapi.json post /messages openapi: 3.1.0 info: title: NinjaChat API version: 1.0.0 description: >- Clean-break NinjaChat v1. Chat and Responses bill actual token usage; images and videos use catalog unit pricing. servers: - url: https://www.ninjachat.ai/api/v1 security: [] paths: /messages: post: summary: Create an Anthropic-compatible message description: >- Messages compatibility for text, image inputs, JSON output schemas, function tools and SSE. Accepts Authorization bearer or x-api-key. Uses the same metered gateway, routing and idempotency as Chat Completions. Native server tools, file IDs and signed thinking history are not supported; unsupported parameters return explicit errors. parameters: - $ref: '#/components/parameters/IdempotencyKey' requestBody: content: application/json: schema: $ref: '#/components/schemas/AnthropicMessagesRequest' responses: '200': description: Anthropic Message object or Messages SSE lifecycle. content: application/json: schema: type: object properties: {} text/event-stream: schema: type: string '400': description: Invalid or unsupported request parameter. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '401': description: Missing or invalid API key. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '402': description: Insufficient balance or project spend limit reached. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '429': description: Rate limit exceeded. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '500': description: Gateway error. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' security: - bearerAuth: [] - anthropicApiKey: [] components: parameters: IdempotencyKey: name: Idempotency-Key in: header required: false schema: type: string minLength: 1 maxLength: 255 description: >- Safely retry the same logical write without duplicate billing or execution. schemas: AnthropicMessagesRequest: type: object properties: model: type: string minLength: 1 maxLength: 160 max_tokens: type: integer exclusiveMinimum: 0 maximum: 9007199254740991 messages: type: array items: type: object properties: role: type: string enum: - user - assistant content: anyOf: - type: string minLength: 1 maxLength: 100000 - type: array items: anyOf: - type: object properties: type: type: string enum: - text text: type: string minLength: 1 maxLength: 100000 required: - type - text additionalProperties: false - type: object properties: type: type: string enum: - image source: oneOf: - type: object properties: type: type: string enum: - url url: type: string format: uri required: - type - url additionalProperties: false - type: object properties: type: type: string enum: - base64 media_type: type: string enum: - image/jpeg - image/png - image/gif - image/webp data: type: string minLength: 1 maxLength: 7000000 required: - type - media_type - data additionalProperties: false required: - type - source additionalProperties: false - type: object properties: type: type: string enum: - document source: oneOf: - type: object properties: type: type: string enum: - base64 media_type: type: string enum: - application/pdf data: type: string minLength: 1 maxLength: 7000000 required: - type - media_type - data additionalProperties: false - type: object properties: type: type: string enum: - url url: type: string maxLength: 4096 format: uri required: - type - url additionalProperties: false - type: object properties: type: type: string enum: - text media_type: type: string enum: - text/plain data: type: string minLength: 1 maxLength: 100000 required: - type - media_type - data additionalProperties: false required: - type - source additionalProperties: false - type: object properties: type: type: string enum: - tool_use id: type: string minLength: 1 maxLength: 128 name: type: string minLength: 1 maxLength: 64 input: type: object additionalProperties: {} required: - type - id - name - input additionalProperties: false - type: object properties: type: type: string enum: - tool_result tool_use_id: type: string minLength: 1 maxLength: 128 content: anyOf: - type: string - type: array items: anyOf: - type: object properties: type: type: string enum: - text text: type: string minLength: 1 maxLength: 100000 required: - type - text additionalProperties: false - type: object properties: type: type: string enum: - image source: oneOf: - type: object properties: type: type: string enum: - url url: type: string format: uri required: - type - url additionalProperties: false - type: object properties: type: type: string enum: - base64 media_type: type: string enum: - image/jpeg - image/png - image/gif - image/webp data: type: string minLength: 1 maxLength: 7000000 required: - type - media_type - data additionalProperties: false required: - type - source additionalProperties: false - type: object properties: type: type: string enum: - document source: oneOf: - type: object properties: type: type: string enum: - base64 media_type: type: string enum: - application/pdf data: type: string minLength: 1 maxLength: 7000000 required: - type - media_type - data additionalProperties: false - type: object properties: type: type: string enum: - url url: type: string maxLength: 4096 format: uri required: - type - url additionalProperties: false - type: object properties: type: type: string enum: - text media_type: type: string enum: - text/plain data: type: string minLength: 1 maxLength: 100000 required: - type - media_type - data additionalProperties: false required: - type - source additionalProperties: false is_error: type: boolean required: - type - tool_use_id additionalProperties: false minItems: 1 maxItems: 100 required: - role - content additionalProperties: false minItems: 1 maxItems: 100 system: anyOf: - type: string - type: array items: type: object properties: type: type: string enum: - text text: type: string minLength: 1 maxLength: 100000 required: - type - text additionalProperties: false stream: type: boolean temperature: type: number minimum: 0 maximum: 1 top_p: type: number minimum: 0 maximum: 1 stop_sequences: type: array items: type: string maxItems: 4 tools: type: array items: type: object properties: name: type: string minLength: 1 maxLength: 64 description: type: string maxLength: 1024 input_schema: type: object additionalProperties: {} strict: type: boolean required: - name - input_schema additionalProperties: false maxItems: 32 tool_choice: anyOf: - type: object properties: type: type: string enum: - auto - any - none disable_parallel_tool_use: type: boolean required: - type additionalProperties: false - type: object properties: type: type: string enum: - tool name: type: string disable_parallel_tool_use: type: boolean required: - type - name additionalProperties: false metadata: type: object properties: user_id: type: string maxLength: 256 additionalProperties: false output_config: type: object properties: format: type: object properties: type: type: string enum: - json_schema schema: type: object additionalProperties: {} required: - type - schema additionalProperties: false required: - format additionalProperties: false routing: $ref: '#/components/schemas/RoutingPolicy' required: - model - max_tokens - messages additionalProperties: false ErrorResponse: type: object properties: error: type: object properties: message: type: string type: type: string code: type: string param: type: - string - 'null' required: - message - type - code additionalProperties: false required: - error additionalProperties: false RoutingPolicy: type: object properties: strategy: type: string enum: - balanced - cost - latency - quality providers: type: object properties: only: type: array items: type: string minLength: 1 maxLength: 128 minItems: 1 maxItems: 20 exclude: type: array items: type: string minLength: 1 maxLength: 128 minItems: 1 maxItems: 20 order: type: array items: type: string minLength: 1 maxLength: 128 minItems: 1 maxItems: 20 additionalProperties: false allow_fallbacks: type: boolean default: true require_parameters: type: boolean default: true data_policy: type: string enum: - default - no_training - zero_retention default: default caching: type: string enum: - auto max_cost_usd: type: number exclusiveMinimum: 0 maximum: 1000 additionalProperties: false securitySchemes: bearerAuth: type: http scheme: bearer bearerFormat: NinjaChat API key description: Use an API key created in the NinjaChat developer console. anthropicApiKey: type: apiKey in: header name: x-api-key description: >- NinjaChat API key accepted by the Anthropic Messages compatibility endpoint. ````