create_agent和tool教程

from langchain.agents import create_agent
from langchain_openai import ChatOpenAI
from langchain_core.tools import tool

@tool
def get_weather(city: str) -> str:
"""获取城市天气"""
return f"{city} 现在晴天，25°C"

model = ChatOpenAI(model="gpt-4o")
agent = create_agent(
model=model,
tools=[get_weather],
prompt="你是一个有用的助手"
)

# 直接调用
result = agent.invoke({
"messages": [{"role": "user", "content": "北京天气怎么样？"}]
})
print(result)