Messages API

First-class inbound Anthropic Messages protocol (anthropic_messages). Owner transformer: Anthropic. Chat Completions, Responses, and FIM are separate inbound routes — see API Overview.

POST /v1/messages

Send messages to LLM, compatible with Anthropic Claude API format.

Request Format

curl -X POST http://localhost:3456/v1/messages \
  -H "x-api-key: your-api-key" \
  -H "content-type: application/json" \
  -d '{
    "model": "claude-3-5-sonnet-20241022",
    "max_tokens": 1024,
    "messages": [
      {
        "role": "user",
        "content": "Hello, Claude!"
      }
    ]
  }'

Request Parameters

Parameter	Type	Required	Description
model	string	Yes	Model name (will be routed to actual provider)
messages	array	Yes	Array of messages
max_tokens	integer	Yes	Maximum tokens to generate
system	string	No	System prompt
tools	array	No	List of available tools
stream	boolean	No	Whether to use streaming response (default false)
temperature	number	No	Temperature parameter (0-1)

Message Object Format

{
  "role": "user|assistant",
  "content": "string | array"
}

Response Format (Non-streaming)

{
  "id": "msg_xxx",
  "type": "message",
  "role": "assistant",
  "content": [
    {
      "type": "text",
      "text": "Hello! How can I help you today?"
    }
  ],
  "model": "claude-3-5-sonnet-20241022",
  "stop_reason": "end_turn",
  "usage": {
    "input_tokens": 10,
    "output_tokens": 20
  }
}

Streaming Response

Set stream: true to enable streaming response:

{
  "model": "claude-3-5-sonnet-20241022",
  "max_tokens": 1024,
  "messages": [...],
  "stream": true
}

Streaming response event types:

• message_start - Message start
• content_block_start - Content block start
• content_block_delta - Content increment
• content_block_stop - Content block end
• message_delta - Message metadata (usage)
• message_stop - Message end

Tool Use

Supports function calling (Tool Use):

{
  "model": "claude-3-5-sonnet-20241022",
  "max_tokens": 1024,
  "messages": [
    {
      "role": "user",
      "content": "What's the weather like?"
    }
  ],
  "tools": [
    {
      "name": "get_weather",
      "description": "Get the current weather",
      "input_schema": {
        "type": "object",
        "properties": {
          "location": {
            "type": "string",
            "description": "City name"
          }
        },
        "required": ["location"]
      }
    }
  ]
}

Multimodal Support

Supports image input:

{
  "role": "user",
  "content": [
    {
      "type": "image",
      "source": {
        "type": "base64",
        "media_type": "image/png",
        "data": "iVBORw0KGgo..."
      }
    },
    {
      "type": "text",
      "text": "Describe this image"
    }
  ]
}

POST /v1/messages/count_tokens

Count tokens in messages.

Request Format

curl -X POST http://localhost:3456/v1/messages/count_tokens \
  -H "x-api-key: your-api-key" \
  -H "content-type: application/json" \
  -d '{
    "model": "claude-3-5-sonnet-20241022",
    "messages": [
      {
        "role": "user",
        "content": "Hello!"
      }
    ],
    "tools": [],
    "system": "You are a helpful assistant."
  }'

Request Parameters

Parameter	Type	Required	Description
model	string	Yes	Model name
messages	array	Yes	Array of messages
tools	array	No	List of tools
system	string	No	System prompt

Response Format

{
  "input_tokens": 42
}

Error Responses

400 Bad Request

{
  "error": {
    "type": "invalid_request_error",
    "message": "messages is required"
  }
}

401 Unauthorized

{
  "error": {
    "type": "authentication_error",
    "message": "Invalid API key"
  }
}

500 Internal Server Error

{
  "error": {
    "type": "api_error",
    "message": "Failed to connect to provider"
  }
}