Chat Completions

Endpoint

POST /v1/chat/completions

Fully compatible with the OpenAI Chat Completions API.

Request body

Parameter	Type	Required	Description
model	string	Yes	Model ID (e.g. gpt-4o-mini, deepseek-chat, kimi-2.5)
messages	array	Yes	Array of message objects
stream	boolean	No	Enable SSE streaming (default: false)
temperature	number	No	Sampling temperature (0–2)
max_tokens	integer	No	Maximum tokens to generate
top_p	number	No	Nucleus sampling parameter
tools	array	No	Tool/function definitions for function calling
tool_choice	string/object	No	Control tool usage (auto, none, or specific tool)

Message format

{
  "role": "user | assistant | system",
  "content": "Message text"
}

Example

curl https://api.cheapestinference.com/v1/chat/completions \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-4o-mini",
    "messages": [
      {"role": "system", "content": "You are a helpful assistant."},
      {"role": "user", "content": "What is the capital of France?"}
    ],
    "temperature": 0.7
  }'

Response

{
  "id": "chatcmpl-abc123",
  "object": "chat.completion",
  "model": "gpt-4o-mini",
  "choices": [
    {
      "index": 0,
      "message": {
        "role": "assistant",
        "content": "The capital of France is Paris."
      },
      "finish_reason": "stop"
    }
  ],
  "usage": {
    "prompt_tokens": 25,
    "completion_tokens": 8,
    "total_tokens": 33
  }
}

Using non-OpenAI models

All models work through the OpenAI endpoint. The API translates the request format automatically:

# DeepSeek
curl https://api.cheapestinference.com/v1/chat/completions \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "deepseek-chat", "messages": [{"role": "user", "content": "Hello"}]}'

# Claude (via OpenAI format)
curl https://api.cheapestinference.com/v1/chat/completions \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "claude-sonnet-4-20250514", "messages": [{"role": "user", "content": "Hello"}]}'

# Kimi
curl https://api.cheapestinference.com/v1/chat/completions \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "kimi-2.5", "messages": [{"role": "user", "content": "Hello"}]}'

Available models

Any model returned by GET /v1/models can be used. See Models for the full list.