Chat Completion

Generate chat completions with various AI models

Endpoint

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

Headers

AuthorizationstringRequired

Bearer token for authentication. Format: Bearer YOUR_API_KEY

Request

This endpoint expects an object.

modelstringRequired

The model ID to use. e.g. openai/gpt-4o-mini

messageslist of objectsRequired

Array of message objects representing the conversation history.

Show 2 properties
rolestringRequired

The role of the message author (system, user, assistant)

contentstringRequired

The content of the message

temperaturenumberOptional

Controls randomness in the output. Range: 0.0 to 2.0. Higher values make output more random.

max_tokensintegerOptional

Maximum number of tokens to generate in the completion.

streambooleanOptional

Whether to stream back partial progress as data-only server-sent events.

top_pnumberOptional

Nucleus sampling parameter. Range: 0.0 to 1.0. Controls diversity via nucleus sampling.

nintegerOptional

How many chat completion choices to generate for each input message.

stopstringOptional

Up to 4 sequences where the API will stop generating further tokens.

presence_penaltynumberOptional

Number between -2.0 and 2.0. Positive values penalize new tokens based on whether they appear in the text so far, increasing the model's likelihood to talk about new topics. See more information about frequency and presence penalties.

frequency_penaltynumberOptional

Number between -2.0 and 2.0. Positive values penalize new tokens based on their existing frequency in the text, decreasing the model's likelihood to repeat the same line verbatim. See more information about frequency and presence penalties.

logit_biasnullOptional

Modify the likelihood of specified tokens appearing in the completion. Accepts a json object that maps tokens (specified by their token ID in the tokenizer) to an associated bias value from -100 to 100. Mathematically, the bias is added to the logits generated by the model prior to sampling. The exact effect will vary per model, but values between -1 and 1 should decrease or increase likelihood of selection; values like -100 or 100 should result in a ban or exclusive selection of the relevant token.

userstringOptional

A unique identifier representing your end-user, which can help OpenAI monitor and detect abuse. Learn more.

Request Example

curl -X POST "https://api.firstrouter.ai/v1/chat/completions" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "messages": [
      {
        "role": "system",
        "content": "You are a helpful assistant."
      },
      {
        "role": "user",
        "content": "Hello, how are you?"
      }
    ],
    "model": "openai/gpt-4o-mini",
    "temperature": 0.7,
    "max_tokens": 150
  }'

Response Example

{
  "id": "chatcmpl-ba101e0655344b54bd5b64be46a6624c",
  "model": "gemini-2.5-flash-preview-05-20",
  "object": "chat.completion",
  "created": 1750777563,
  "choices": [
    {
      "index": 0,
      "message": {
        "role": "assistant",
        "content": "✋ High five! Right back at ya!",
        "reasoning_content": "That covers the visual with the emoji, and answers appropriately."
      },
      "finish_reason": "stop"
    }
  ],
  "usage": {
    "prompt_tokens": 6,
    "completion_tokens": 445,
    "total_tokens": 451,
    "prompt_tokens_details": {
      "cached_tokens": 0,
      "text_tokens": 6,
      "audio_tokens": 0,
      "image_tokens": 0
    },
    "completion_tokens_details": {
      "text_tokens": 0,
      "audio_tokens": 0,
      "reasoning_tokens": 436
    },
    "input_tokens": 0,
    "output_tokens": 0,
    "input_tokens_details": null
  }
}