开放模型的函数调用

函数调用功能可让模型识别何时调用外部工具或 API，然后生成包含必要函数和参数的结构化数据以供执行。Vertex AI 模型即服务 (MaaS) 上提供的所有开放模型均支持函数调用。

如需详细了解函数调用功能的概念性信息，请参阅函数调用简介。

使用函数调用

以下应用场景集成了外部气象 API，用于检查给定位置的当前天气。该代码使用 REST 调用来比较两个城市的天气，其中使用了一个在 tools 内的架构中声明的 get_current_weather 函数。

{
  "model": "MODEL_NAME",
  "messages": [
    {
      "role": "user",
      "content": "Which city has a higher temperature, Boston or new Delhi, and by how much in F?"
    }
  ],
  "tools": [
    {
      "type": "function",
      "function": {
        "name": "get_current_weather",
        "description": "Get the current weather in a given location",
        "parameters": {
          "type": "object",
          "properties": {
            "location": {
              "type": "string",
              "description": "The city and state, e.g. San Francisco, CA"
            },
            "unit": {
              "type": "string",
              "enum": ["celsius", "fahrenheit"]
            }
          },
          "required": ["location"]
        }
      }
    }
  ],
  "tool_choice": "auto"
}

收到请求后，模型确定它需要 get_current_weather 函数的输出，并在 tool_calls 中提供必要的函数和参数。

用于检索波士顿天气的函数调用：

{"function":{"arguments":"{\"location\":\"Boston, MA\",\"unit\":\"fahrenheit\"}","name":"get_current_weather"} "id":"get_current_weather","type":"function"}

用于检索新德里天气的函数调用：

{"function":{"arguments":"{\"location\":\"New Delhi, India\",\"unit\":\"fahrenheit\"}","name":"get_current_weather"},"id":"get_current_weather","type":"function"}

详细示例

以前面的示例为基础，下面显示了使用 get_current_weather 函数提取气象信息后可能获得的完整输出。

{
  "model": "MODEL_NAME",
  "messages": [
    {
      "role": "user",
      "content": "Which city has a higher temperature, Boston or new Delhi and by how much in F?"
    },
    {
      "role": "assistant",
      "content": "I'll check the current temperatures for Boston and New Delhi in Fahrenheit and compare them. I'll call the weather function for both cities.",
      "tool_calls": [{"function":{"arguments":"{\"location\":\"Boston, MA\",\"unit\":\"fahrenheit\"}","name":"get_current_weather"},"id":"get_current_weather","type":"function"},{"function":{"arguments":"{\"location\":\"New Delhi, India\",\"unit\":\"fahrenheit\"}","name":"get_current_weather"},"id":"get_current_weather","type":"function"}]
    },
    {
      "role": "tool",
      "content": "The temperature in Boston is 75 degrees Fahrenheit.",
      "tool_call_id": "get_weather"
    },
    {
      "role": "tool",
      "content": "The temperature in New Delhi is 50 degrees Fahrenheit.",
      "tool_call_id": "get_weather"
    }
  ],
  "tools": [
    {
      "type": "function",
      "function": {
        "name": "get_current_weather",
        "description": "Get the current weather in a given location",
        "parameters": {
          "type": "object",
          "properties": {
            "location": {
              "type": "string",
              "description": "The city and state, e.g. San Francisco, CA"
            },
            "unit": {
              "type": "string",
              "enum": ["celsius", "fahrenheit"]
            }
          },
          "required": ["location"]
        }
      }
    }
  ],
  "tool_choice": "auto"
}

在收到通过调用外部 get_current_weather 函数检索到的信息后，模型可以综合来自两个 tool ���应的信息，并回答用户的问题。

以下是该模型输出的示例：

{
 "choices": [
  {
   "finish_reason": "stop",
   "index": 0,
   "logprobs": null,
   "message": {
    "content": "Based on the current weather data:\n\n- **Boston, MA**: 75°F
    \n- **New Delhi, India**: 50°F  \n\n**Comparison**:
    \nBoston is **25°F warmer** than New Delhi.  \n\n**Answer**:
    \nBoston has a higher temperature than New Delhi by 25 degrees Fahrenheit.",
    "role": "assistant"
   }
  }
 ],
 "created": 1750450289,
 "id": "2025-06-20|13:11:29.240295-07|6.230.75.101|-987540014",
 "model": "MODEL_NAME",
 "object": "chat.completion",
 "system_fingerprint": "",
 "usage": {
  "completion_tokens": 66,
  "prompt_tokens": 217,
  "total_tokens": 283
 }
}