Function Calling：让 AI 调用外部工具

const response = await openai.chat.completions.create({
  model: 'gpt-4',
  messages: [...],
  tools: [{
    type: 'function',
    function: {
      name: 'search',
      description: '搜索网页',
      parameters: { type: 'object', properties: { q: { type: 'string' } } }
    }
  }]
});

async function search(q) {
  return await webSearch(q);
}