OpenAI chat format

{
  "model": "gemini-3-pro-image-preview",
  "stream": false,
  "messages": [
    {
      "role": "user",
      "content": "draw a cat"
    }
  ],
  "extra_body": {
    "google": {
      "image_config": {
        "aspect_ratio": "16:9",
        "image_size": "2K"
      }
    }
  }
}

{
  "id": "chatcmpl-20251211...",
  "model": "gemini-3-pro-image-preview",
  "object": "chat.completion",
  "created": 1765440499,
  "choices": [
    {
      "index": 0,
      "message": {
        "role": "assistant",
        "content": "![image](data:image/jpeg;base64,/9j/4AAQSk...)"
      },
      "finish_reason": "stop"
    }
  ],
  "usage": {
    "prompt_tokens": 4,
    "completion_tokens": 1359,
    "total_tokens": 1363
  }
}