--- title: "Structured Output /v1/messages" url: "/docs/anthropic_unified/structured_output" canonical_url: "https://docs.litellm.ai/docs/anthropic_unified/structured_output" type: "docs" last_updated: "2026-10-09" summary: "Use LiteLLM to call Anthropic's structured output feature via the /v1/messages endpoint." related: - "/docs/anthropic_unified/" - "/docs/anthropic_unified/messages_to_responses_mapping" --- # Structured Output /v1/messages > Index of all LiteLLM docs: https://docs.litellm.ai/llms.txt Use LiteLLM to call Anthropic's structured output feature via the `/v1/messages` endpoint. ## Supported Providers | Provider | Supported | Notes | |----------|-----------|-------| | Anthropic | ✅ | Native support | | Azure AI (Anthropic models) | ✅ | Claude models on Azure AI | | Bedrock (Converse Anthropic models) | ✅ | Claude models via Bedrock Converse API | | Bedrock (Invoke Anthropic models) | ✅ | Claude models via Bedrock Invoke API | ## Usage ### LiteLLM Proxy Server **Anthropic** 1. Setup config.yaml ```yaml model_list: - model_name: claude-sonnet litellm_params: model: anthropic/claude-sonnet-5 api_key: os.environ/ANTHROPIC_API_KEY ``` 2. Start proxy ```bash litellm --config /path/to/config.yaml ``` 3. Test it! ```bash curl http://localhost:4000/v1/messages \ -H "Content-Type: application/json" \ -H "Authorization: Bearer $LITELLM_API_KEY" \ -H "anthropic-version: 2023-06-01" \ -d '{ "model": "claude-sonnet", "max_tokens": 1024, "messages": [ { "role": "user", "content": "Extract the key information from this email: John Smith (john@example.com) is interested in our Enterprise plan and wants to schedule a demo for next Tuesday at 2pm." } ], "output_format": { "type": "json_schema", "schema": { "type": "object", "properties": { "name": {"type": "string"}, "email": {"type": "string"}, "plan_interest": {"type": "string"}, "demo_requested": {"type": "boolean"} }, "required": ["name", "email", "plan_interest", "demo_requested"], "additionalProperties": false } } }' ``` **Azure AI (Anthropic)** 1. Setup config.yaml ```yaml model_list: - model_name: azure-claude-sonnet litellm_params: model: azure_ai/claude-sonnet-5 api_key: os.environ/AZURE_AI_API_KEY api_base: https://your-endpoint.inference.ai.azure.com ``` 2. Start proxy ```bash litellm --config /path/to/config.yaml ``` 3. Test it! ```bash curl http://localhost:4000/v1/messages \ -H "Content-Type: application/json" \ -H "Authorization: Bearer $LITELLM_API_KEY" \ -H "anthropic-version: 2023-06-01" \ -d '{ "model": "azure-claude-sonnet", "max_tokens": 1024, "messages": [ { "role": "user", "content": "Extract the key information from this email: John Smith (john@example.com) is interested in our Enterprise plan and wants to schedule a demo for next Tuesday at 2pm." } ], "output_format": { "type": "json_schema", "schema": { "type": "object", "properties": { "name": {"type": "string"}, "email": {"type": "string"}, "plan_interest": {"type": "string"}, "demo_requested": {"type": "boolean"} }, "required": ["name", "email", "plan_interest", "demo_requested"], "additionalProperties": false } } }' ``` **Bedrock (Converse)** 1. Setup config.yaml ```yaml model_list: - model_name: bedrock-claude-sonnet litellm_params: model: bedrock/global.anthropic.claude-sonnet-5 aws_access_key_id: os.environ/AWS_ACCESS_KEY_ID aws_secret_access_key: os.environ/AWS_SECRET_ACCESS_KEY aws_region_name: us-west-2 ``` 2. Start proxy ```bash litellm --config /path/to/config.yaml ``` 3. Test it! ```bash curl http://localhost:4000/v1/messages \ -H "Content-Type: application/json" \ -H "Authorization: Bearer $LITELLM_API_KEY" \ -H "anthropic-version: 2023-06-01" \ -d '{ "model": "bedrock-claude-sonnet", "max_tokens": 1024, "messages": [ { "role": "user", "content": "Extract the key information from this email: John Smith (john@example.com) is interested in our Enterprise plan and wants to schedule a demo for next Tuesday at 2pm." } ], "output_format": { "type": "json_schema", "schema": { "type": "object", "properties": { "name": {"type": "string"}, "email": {"type": "string"}, "plan_interest": {"type": "string"}, "demo_requested": {"type": "boolean"} }, "required": ["name", "email", "plan_interest", "demo_requested"], "additionalProperties": false } } }' ``` **Bedrock (Invoke)** 1. Setup config.yaml ```yaml model_list: - model_name: bedrock-claude-invoke litellm_params: model: bedrock/invoke/global.anthropic.claude-sonnet-5 aws_access_key_id: os.environ/AWS_ACCESS_KEY_ID aws_secret_access_key: os.environ/AWS_SECRET_ACCESS_KEY aws_region_name: us-west-2 ``` 2. Start proxy ```bash litellm --config /path/to/config.yaml ``` 3. Test it! ```bash curl http://localhost:4000/v1/messages \ -H "Content-Type: application/json" \ -H "Authorization: Bearer $LITELLM_API_KEY" \ -H "anthropic-version: 2023-06-01" \ -d '{ "model": "bedrock-claude-invoke", "max_tokens": 1024, "messages": [ { "role": "user", "content": "Extract the key information from this email: John Smith (john@example.com) is interested in our Enterprise plan and wants to schedule a demo for next Tuesday at 2pm." } ], "output_format": { "type": "json_schema", "schema": { "type": "object", "properties": { "name": {"type": "string"}, "email": {"type": "string"}, "plan_interest": {"type": "string"}, "demo_requested": {"type": "boolean"} }, "required": ["name", "email", "plan_interest", "demo_requested"], "additionalProperties": false } } }' ``` ## Example Response ```json { "id": "msg_01XFDUDYJgAACzvnptvVoYEL", "type": "message", "role": "assistant", "content": [ { "type": "text", "text": "{\"name\":\"John Smith\",\"email\":\"john@example.com\",\"plan_interest\":\"Enterprise\",\"demo_requested\":true}" } ], "model": "claude-sonnet-5", "stop_reason": "end_turn", "stop_sequence": null, "usage": { "input_tokens": 75, "output_tokens": 28 } } ``` ## Request Format ### output_format The `output_format` parameter specifies the structured output format. ```json { "output_format": { "type": "json_schema", "schema": { "type": "object", "properties": { "field_name": {"type": "string"}, "another_field": {"type": "integer"} }, "required": ["field_name", "another_field"], "additionalProperties": false } } } ``` #### Fields - **type** (string): Must be `"json_schema"` - **schema** (object): A JSON Schema object defining the expected output structure - **type** (string): The root type, typically `"object"` - **properties** (object): Defines the fields and their types - **required** (array): List of required field names - **additionalProperties** (boolean): Set to `false` to enforce strict schema adherence ## Related pages - [/v1/messages](https://docs.litellm.ai/docs/anthropic_unified/index.md) - [v1/messages → /responses Parameter Mapping](https://docs.litellm.ai/docs/anthropic_unified/messages_to_responses_mapping.md)