Messages

/v1/messages is the Anthropic Messages compatible entrypoint for Claude Code and Anthropic protocol clients. The requested model must be available to the current API key.

Interface

Item	Value
Method	POST
Path	/v1/messages
Content-Type	application/json
Authentication	Authorization: Bearer YOUR_API_KEY

Request Parameters

Parameter	Type	Required	Description
model	string	Yes	Requested model.
messages	array	Yes	Anthropic Messages style message array.
max_tokens	integer	Usually	Maximum output tokens.
system	string or array	No	System prompt.
stream	boolean	No	Whether to stream the response.
thinking	object	No	Reasoning configuration, applied by model and platform capability.
metadata.user_id	string	No	Can be used for sticky sessions and request tracking.

Request Example

curl https://api.llmapi.site/v1/messages \
  -H 'Authorization: Bearer YOUR_API_KEY' \
  -H 'Content-Type: application/json' \
  -d '{
    "model": "claude-sonnet-4-5",
    "max_tokens": 512,
    "messages": [
      { "role": "user", "content": "Summarize this request." }
    ]
  }'

Response — 200 OK

{
  "id": "msg_123",
  "type": "message",
  "role": "assistant",
  "model": "claude-sonnet-4-5",
  "content": [
    {
      "type": "text",
      "text": "Summary text."
    }
  ],
  "stop_reason": "end_turn",
  "usage": {
    "input_tokens": 24,
    "output_tokens": 12
  }
}

When stream is true, the response uses Anthropic-compatible event streaming.

Token Count

/v1/messages/count_tokens provides Anthropic token counting. It checks subscription and balance, but does not acquire concurrency or record usage.

Item	Value
Method	POST
Path	/v1/messages/count_tokens
Content-Type	application/json
Restriction	Not supported for OpenAI platform groups

Request example:

curl https://api.llmapi.site/v1/messages/count_tokens \
  -H 'Authorization: Bearer YOUR_API_KEY' \
  -H 'Content-Type: application/json' \
  -d '{
    "model": "claude-sonnet-4-5",
    "messages": [
      { "role": "user", "content": "Hello" }
    ]
  }'

OpenAI group response example:

{
  "type": "error",
  "error": {
    "type": "not_found_error",
    "message": "Token counting is not supported for this platform"
  }
}

Successful token count response:

{
  "input_tokens": 42
}

Errors

Status	Cause
400	Request body, model, or message payload is invalid.
401	API key is missing or invalid.
403	Balance, quota, group, or subscription check failed.
404	Endpoint is not available for the current platform, or the requested model is unavailable.
429	Rate limit or concurrency limit was reached.
500 / 502 / 503	Gateway or upstream provider failed.