POST /v1/messages

Authentication

x-api-key: mg_live_...
anthropic-version: 2023-06-01
content-type: application/json

Bearer authentication is also accepted.

Request

curl https://api.model-gate.com/v1/messages \
  -H "x-api-key: mg_live_..." \
  -H "anthropic-version: 2023-06-01" \
  -H "content-type: application/json" \
  -d '{
    "model": "claude-sonnet-4.6",
    "max_tokens": 1024,
    "messages": [
      {"role": "user", "content": "Write a short release note."}
    ]
  }'

Response

{
  "id": "msg_example",
  "type": "message",
  "role": "assistant",
  "model": "claude-sonnet-4.6",
  "content": [{"type": "text", "text": "This release improves documentation and model routing."}],
  "stop_reason": "end_turn",
  "usage": {
    "input_tokens": 11,
    "output_tokens": 9,
    "cache_creation_input_tokens": 0,
    "cache_read_input_tokens": 0
  }
}

Streaming

Add "stream": true. Model Gate forwards Anthropic-compatible SSE events and records the final token usage for settlement.

Aliases and accounting

If an alias is supplied, it is replaced with the canonical model before the request is queued or sent upstream. Pricing, usage cost, request history, and model restrictions use the canonical model.

Status	Meaning	Action
400	Invalid request	Check the request body and model ID.
401	Invalid or frozen key	Verify or rotate the API key.
429	Rate or concurrency limit exceeded	Respect Retry-After and retry with backoff.
5xx	Temporary upstream or gateway error	Retry idempotent requests with exponential backoff.