Reference

Headers, objects, and conventions.

This page documents shared conventions across endpoints: HTTP headers, error envelopes, common object shapes, and compatibility notes.

HTTP headers

Required

Authorization: Bearer $LMCHAT_API_KEY
Content-Type: application/json

Recommended

HTTP-Referer: https://yourapp.com
X-Title: YourAppName

# For safe retries (where supported):
Idempotency-Key: 550e8400-e29b-41d4-a716-446655440000

Error envelope

Shape

Errors follow an OpenAI-style envelope where possible.

{
  "error": {
    "message": "Human-readable message",
    "type": "invalid_request_error | authentication_error | rate_limit_error | api_error",
    "code": "machine_readable_code"
  }
}

Usage object

Tokens accounting

Usage reporting typically includes prompt, completion, and total tokens. Some providers may report additional fields; clients should ignore unknown properties.

"usage": {
  "prompt_tokens": 123,
  "completion_tokens": 45,
  "total_tokens": 168
}

Chat message object

Roles

Typical roles are system, user, assistant, and tool.

{
  "role": "user",
  "content": "Hello"
}

Compatibility notes

Most SDKs work by overriding baseURL and providing a key.
Not all models support all features (tools, vision, JSON mode).
Streaming uses SSE and ends with [DONE].
Clients should be tolerant to additional fields and provider-specific metadata.