> ## Documentation Index > Fetch the complete documentation index at: https://docs.aihubmax.com/llms.txt > Use this file to discover all available pages before exploring further. # Claude Format - Tool Calling Messages > - Generic Anthropic Messages API reference with tool calling for all compatible models - Tool calling: supports Function Calling with tool definitions - Multimodal input: supports text + image mixed input - Extended thinking: supports thinking/reasoning mode - Supports streaming and non-streaming responses ## OpenAPI ````yaml openapi/en/claude-format-tool-calling-messages.json POST /v1/messages openapi: 3.1.0 info: title: Claude Format - Tool Calling Messages version: '1.0' servers: - url: https://api.aihubmax.com security: - BearerAuth: [] paths: /v1/messages: post: tags: - Text Series > Claude Format summary: Claude Format - Tool Calling Messages description: > - Generic Anthropic Messages API reference with tool calling for all compatible models - Tool calling: supports Function Calling with tool definitions - Multimodal input: supports text + image mixed input - Extended thinking: supports thinking/reasoning mode - Supports streaming and non-streaming responses operationId: claude-format-tool-calling-messages requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/ClaudeMessagesRequest' examples: tool-calling-weather: summary: Weather Query description: Let the model call a weather tool value: model: claude-sonnet-4-6 max_tokens: 1024 messages: - role: user content: >- What's the weather like in San Francisco now? Is it good for the beach? tools: - name: get_weather description: Get current weather for a specified city input_schema: type: object properties: city: type: string description: City name unit: type: string enum: - celsius - fahrenheit description: Temperature unit required: - city tool-calling-search: summary: Web Search description: Let the model call a search tool to find information value: model: claude-sonnet-4-6 max_tokens: 2048 messages: - role: user content: Search for the latest features in React 19 tools: - name: web_search description: Search the internet for latest information input_schema: type: object properties: query: type: string description: Search keywords num_results: type: integer description: Number of results default: 5 required: - query tool-calling-multi-tools: summary: Multiple Tools description: Define multiple tools for the model to choose from value: model: claude-sonnet-4-6 max_tokens: 2048 messages: - role: user content: >- Check tomorrow's weather in New York, then create an outdoor running event on my calendar tools: - name: get_weather description: Get weather forecast input_schema: type: object properties: city: type: string description: City name days: type: integer description: Forecast days (1-7) required: - city - name: create_calendar_event description: Create a calendar event input_schema: type: object properties: title: type: string description: Event title date: type: string description: Date (YYYY-MM-DD) time: type: string description: Time (HH:MM) duration_minutes: type: integer description: Duration in minutes required: - title - date tool-calling-send-email: summary: Send Email description: Let the model call an email sending tool value: model: claude-sonnet-4-6 max_tokens: 1024 messages: - role: user content: >- Send an email to the team notifying them about a product review meeting tomorrow at 3 PM tools: - name: send_email description: Send an email input_schema: type: object properties: to: type: array items: type: string description: Recipients list subject: type: string description: Email subject body: type: string description: Email body cc: type: array items: type: string description: CC list required: - to - subject - body responses: '200': $ref: '#/components/responses/ClaudeMessagesSuccess' '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/Unauthorized' '402': $ref: '#/components/responses/PaymentRequired' '403': $ref: '#/components/responses/Forbidden' '429': $ref: '#/components/responses/TooManyRequests' '500': $ref: '#/components/responses/InternalServerError' components: schemas: ClaudeMessagesRequest: type: object required: - model - messages - max_tokens properties: model: type: string description: Model name, e.g. claude-sonnet-4-6 example: claude-sonnet-4-6 messages: type: array description: List of messages in the conversation items: type: object required: - role - content properties: role: type: string description: Role of the message sender enum: - user - assistant content: type: string description: Content of the message (string or array of content blocks) max_tokens: type: integer description: Maximum number of tokens to generate (required) system: oneOf: - type: string description: System prompt as a string - type: array description: System prompt as an array of content blocks items: type: object properties: type: type: string enum: - text text: type: string description: System prompt temperature: type: number description: Sampling temperature (0-1) minimum: 0 maximum: 1 top_p: type: number description: Nucleus sampling parameter (0-1) minimum: 0 maximum: 1 top_k: type: integer description: Top-K sampling parameter stream: type: boolean description: Whether to stream the response default: false stop_sequences: type: array description: Custom stop sequences that will cause the model to stop generating items: type: string tools: type: array description: List of tools the model may use items: type: object properties: name: type: string description: Tool name description: type: string description: Tool description input_schema: type: object description: JSON Schema for the tool input tool_choice: type: object description: How the model should use the provided tools properties: type: type: string description: Tool choice type enum: - auto - any - tool name: type: string description: Tool name (when type is 'tool') metadata: type: object description: Request metadata properties: user_id: type: string description: External user ID for abuse detection ClaudeMessagesResponse: type: object properties: id: type: string description: Unique message ID example: msg_abc123 type: type: string description: Object type enum: - message role: type: string description: Role enum: - assistant content: type: array description: Response content blocks items: type: object properties: type: type: string enum: - text text: type: string example: Hello! How can I help you today? model: type: string description: Model used stop_reason: type: string description: Reason the generation stopped enum: - end_turn - max_tokens - stop_sequence - tool_use example: end_turn usage: type: object description: Token usage statistics properties: input_tokens: type: integer description: Number of input tokens example: 25 output_tokens: type: integer description: Number of output tokens example: 150 ErrorResponse400: type: object properties: error: type: object properties: message: type: string example: Invalid request parameters type: type: string example: invalid_request_error ErrorResponse401: type: object properties: error: type: object properties: message: type: string example: Invalid API key type: type: string example: authentication_error ErrorResponse403: type: object properties: error: type: object properties: message: type: string example: Access denied type: type: string example: permission_error ErrorResponse429: type: object properties: error: type: object properties: message: type: string example: Rate limit exceeded type: type: string example: rate_limit_error ErrorResponse500: type: object properties: error: type: object properties: message: type: string example: Internal server error type: type: string example: server_error responses: ClaudeMessagesSuccess: description: Claude Messages API response content: application/json: schema: $ref: '#/components/schemas/ClaudeMessagesResponse' BadRequest: description: Bad Request content: application/json: schema: $ref: '#/components/schemas/ErrorResponse400' Unauthorized: description: Unauthorized content: application/json: schema: $ref: '#/components/schemas/ErrorResponse401' PaymentRequired: description: Insufficient balance content: application/json: schema: $ref: '#/components/schemas/ErrorResponse400' Forbidden: description: Forbidden content: application/json: schema: $ref: '#/components/schemas/ErrorResponse403' TooManyRequests: description: Too Many Requests content: application/json: schema: $ref: '#/components/schemas/ErrorResponse429' InternalServerError: description: Internal Server Error content: application/json: schema: $ref: '#/components/schemas/ErrorResponse500' securitySchemes: BearerAuth: type: http scheme: bearer description: | ## All APIs require Bearer Token authentication ## Add to request header: `Authorization: Bearer YOUR_API_KEY` ````