{
  "model": "claude-opus-5",
  "messages": [
    {"role": "user", "content": [
      {"type": "text", "text": "What is in this image?"},
      {"type": "image", "source": {"type": "base64", "media_type": "image/png", "data": "iVBORw0KGgoAAAANSUhEUgAAAAEAAAAB"}}
    ]}
  ],
  "max_tokens": 300
}