Chat

Overview

chat/completions is the most common API interface for LLMs, taking a conversation list composed of multiple messages as input to get responses from the LLM model.

Important Notes

⚠️ Model Variability
Different model providers may support different request parameters and return different response fields. We strongly recommend checking the official documentation of the respective model provider to understand the complete parameter list and usage methods.

⚠️ Response Pass-through Principle
CometAPI typically does not modify model response results outside of reverse-engineered formats, ensuring you receive response content consistent with the original API.

Reference Documentation

For more detailed information about the chat/completions interface, please refer to the OpenAI Official Documentation.

OpenAI Related Guides:

Conversation State Management

API Reference

Request Parameters

Required Parameters

model string required
Specifies the model ID to use for generating responses.

{
  "model": "gpt-4"
}

messages array required
A list of conversation messages containing roles and content. Each message must include:

role string - The role of the message, possible values:

system - System message, used to set assistant behavior

user - User message

assistant - Assistant's historical replies

content string - The specific content of the message

{
  "messages": [
    {
      "role": "system",
      "content": "You are a professional AI assistant"
    },
    {
      "role": "user",
      "content": "What is machine learning?"
    }
  ]
}

Optional Parameters

stream boolean optional
Whether to enable streaming responses. When set to true, responses will be returned incrementally in the form of Server-Sent Events (SSE).

Default: false

{
  "stream": true
}

temperature number optional
Controls the randomness of responses, range 0-2.

Lower values (e.g., 0.2): more deterministic and focused

Higher values (e.g., 1.8): more random and creative

Default: 1.0

max_tokens integer optional
Limits the maximum number of tokens to generate.

top_p number optional
Nucleus sampling parameter, range 0-1. It's recommended not to adjust both temperature and top_p simultaneously.

Frequently Asked Questions

How to handle rate limits?

When encountering 429 Too Many Requests, implement exponential backoff retry:

How to maintain conversation context?

Include the complete conversation history in the messages array:

What does finish_reason mean?

Value	Meaning
`stop`	Natural completion
`length`	Reached max_tokens limit
`content_filter`	Triggered content filter
`function_call`	Model called a function

How to control costs?

Use max_tokens to limit output length

Choose appropriate models (e.g., gpt-3.5-turbo is more economical)

Simplify prompts and avoid redundant context

Monitor token consumption in the usage field

curl --location --request POST 'https://api.cometapi.com/v1/chat/completions' \ --header 'Authorization: Bearer {{api-key}}' \ --header 'Content-Type: application/json' \ --data-raw '{ "model": "gpt-5-mini", "messages": [ { "role": "user", "content": "Hello!" } ], "stream": false }'

{ "id": "chatcmpl-AreYSBEwmzB0kY3GxzBEhE1Olct83", "object": "chat.completion", "created": 1737350640, "model": "gpt-4o-2024-08-06", "system_fingerprint": "fp_f3927aa00d", "choices": [ { "index": 0, "message": { "content": "Hello! How can I assist you today?", "role": "assistant" }, "finish_reason": "stop" } ], "usage": { "completion_tokens": 9, "completion_tokens_details": {}, "prompt_tokens": 9, "prompt_tokens_details": {}, "total_tokens": 18 } }

Overview#

Important Notes#

Reference Documentation#

API Reference#

Request Parameters#

Required Parameters#

Optional Parameters#

Frequently Asked Questions#

How to handle rate limits?#

How to maintain conversation context?#

What does finish_reason mean?#

How to control costs?#

Request

Responses