Vision

{
  "model": "gpt-5.5",
  "messages": [
    {
      "role": "user",
      "content": [
        { "type": "text", "text": "What changed in this screenshot?" },
        {
          "type": "image_url",
          "image_url": {
            "url": "data:image/png;base64,...",
            "detail": "auto"
          }
        }
      ]
    }
  ]
}