手写一个最小 Agent：50 行代码搞懂工具调用循环

pip install openai

export OPENAI_API_KEY="sk-xxx"
# 如果用国内服务，还需要设置 base url
export OPENAI_BASE_URL="https://api.deepseek.com/v1"

import json
import math

# ---- 工具实现 ----
def search(query: str) -> str:
    """模拟搜索，实际项目替换成真 API"""
    results = {
        "Python": "Python 是一种广泛使用的高级编程语言，由 Guido van Rossum 于 1991 年创建",
        "Agent": "AI Agent 是能自主感知环境、做出决策并执行动作的智能体",
        "天气": "今天北京晴，25°C；上海多云，28°C",
    }
    for key, val in results.items():
        if key in query:
            return val
    return f"未找到关于「{query}」的结果"

def calculator(expression: str) -> str:
    """安全计算数学表达式"""
    try:
        allowed = set("0123456789+-*/.() ")
        if not all(c in allowed for c in expression):
            return "错误：只支持数字和 +-*/ 运算符"
        return str(eval(expression))
    except Exception as e:
        return f"计算错误：{e}"

def read_file(filepath: str) -> str:
    """读取本地文件内容"""
    try:
        with open(filepath, "r", encoding="utf-8") as f:
            return f.read()[:2000]  # 最多读 2000 字符
    except FileNotFoundError:
        return f"文件不存在：{filepath}"
    except Exception as e:
        return f"读取错误：{e}"

# ---- 工具注册表 ----
TOOLS = [
    {
        "type": "function",
        "function": {
            "name": "search",
            "description": "搜索信息，获取知识。当需要查找你不确定的事实、数据或信息时使用。",
            "parameters": {
                "type": "object",
                "properties": {
                    "query": {"type": "string", "description": "搜索关键词"}
                },
                "required": ["query"]
            }
        }
    },
    {
        "type": "function",
        "function": {
            "name": "calculator",
            "description": "计算数学表达式。当需要精确计算时使用，如加减乘除。",
            "parameters": {
                "type": "object",
                "properties": {
                    "expression": {"type": "string", "description": "数学表达式，如 2+3*4"}
                },
                "required": ["expression"]
            }
        }
    },
    {
        "type": "function",
        "function": {
            "name": "read_file",
            "description": "读取本地文件内容。当需要查看文件内容时使用。",
            "parameters": {
                "type": "object",
                "properties": {
                    "filepath": {"type": "string", "description": "文件路径"}
                },
                "required": ["filepath"]
            }
        }
    }
]

TOOL_MAP = {
    "search": search,
    "calculator": calculator,
    "read_file": read_file,
}

from openai import OpenAI

client = OpenAI()  # 自动读取 OPENAI_API_KEY 和 OPENAI_BASE_URL

def agent(user_input: str, max_steps: int = 10) -> str:
    """最小 Agent：工具调用循环"""
    messages = [{"role": "user", "content": user_input}]

    for step in range(max_steps):
        print(f"--- Step {step + 1} ---")

        try:
            # Think：调用 LLM
            response = client.chat.completions.create(
                model="gpt-4o-mini",  # 可替换成其他模型
                messages=messages,
                tools=TOOLS,
                tool_choice="auto",
            )
        except Exception as e:
            return f"LLM 调用失败：{e}"

        choice = response.choices[0]
        message = choice.message

        # 把助手回复加入历史
        messages.append(message)

        # 如果没有工具调用，说明 LLM 给出了最终答案
        if not message.tool_calls:
            return message.content

        # Act：执行所有工具调用
        for tool_call in message.tool_calls:
            func_name = tool_call.function.name
            func_args = json.loads(tool_call.function.arguments)

            print(f"  调用工具：{func_name}({func_args})")

            try:
                result = TOOL_MAP[func_name](**func_args)
            except Exception as e:
                result = f"工具执行错误：{e}"

            print(f"  工具结果：{result[:100]}")

            # 把工具结果喂回 LLM
            messages.append({
                "role": "tool",
                "tool_call_id": tool_call.id,
                "content": str(result),
            })

    return "⚠️ 达到最大步数限制，Agent 终止"

# 简单计算
print(agent("123 * 456 等于多少？"))

# 搜索 + 计算
print(agent("Python 是什么时候创建的？距今多少年了？"))

# 读取文件
print(agent("帮我看看 hugo.toml 的前几行内容"))