Chat Completions API - Developer Docs

Endpoint

POST https://api.uniontoken.ai/v1/chat/completions

Request Example

{
  "model": "anthropic/claude-opus-4-6",
  "messages": [
    {"role": "system", "content": "You are a helpful assistant"},
    {"role": "user", "content": "What is a large language model?"}
  ],
  "temperature": 0.7,
  "max_tokens": 1024
}

Main Parameters

Parameter	Type	Description
model	string	Model identifier, format: provider/model-name
messages	array	Message list
temperature	float	Randomness, 0-2, default 0.7
max_tokens	int	Max output tokens
stream	boolean	Enable streaming (SSE)

Response Example

{
  "id": "chatcmpl-xxx",
  "object": "chat.completion",
  "model": "anthropic/claude-opus-4-6",
  "choices": [{
    "index": 0,
    "message": {"role": "assistant", "content": "A large language model is..."},
    "finish_reason": "stop"
  }],
  "usage": {
    "prompt_tokens": 20,
    "completion_tokens": 150,
    "total_tokens": 170
  }
}

Streaming (SSE)

Set stream: true to enable Server-Sent Events streaming:

{
  "model": "anthropic/claude-opus-4-6",
  "messages": [{"role": "user", "content": "Write a poem"}],
  "stream": true
}