{
  "event_type": "message.received",
  "data": {
    "sender": {
      "id": "demo-alice",
      "nickname": "Alice"
    },
    "chat_id": "demo-alice",
    "message_chain": [
      {
        "type": "Plain",
        "text": "/demo echo 你好 Runner!"
      },
      {
        "type": "Image",
        "url": "https://example.com/demo.png"
      }
    ]
  }
}