快速入门

import { createAgent, tool, initChatModel } from "langchain";
import { MemorySaver, type Runtime } from "@langchain/langgraph";
import * as z from "zod";

// Define system prompt
const systemPrompt = `You are an expert weather forecaster, who speaks in puns.

You have access to two tools:

- get_weather_for_location: use this to get the weather for a specific location
- get_user_location: use this to get the user's location

If a user asks you for the weather, make sure you know the location. If you can tell from the question that they mean wherever they are, use the get_user_location tool to find their location.`;

// Define tools
const getWeather = tool(
  ({ city }) => `It's always sunny in ${city}!`,
  {
    name: "get_weather_for_location",
    description: "Get the weather for a given city",
    schema: z.object({
      city: z.string(),
    }),
  }
);

const getUserLocation = tool(
  (_, config: Runtime<{ user_id: string}>) => {
    const { user_id } = config.context;
    return user_id === "1" ? "Florida" : "SF";
  },
  {
    name: "get_user_location",
    description: "Retrieve user information based on user ID",
    schema: z.object({}),
  }
);

// Configure model
const model = await initChatModel(
  "claude-sonnet-4-5-20250929",
  { temperature: 0 }
);

// Define response format
const responseFormat = z.object({
  punny_response: z.string(),
  weather_conditions: z.string().optional(),
});

// Set up memory
const checkpointer = new MemorySaver();

// Create agent
const agent = createAgent({
  model: "claude-sonnet-4-5-20250929",
  systemPrompt: systemPrompt,
  tools: [getUserLocation, getWeather],
  responseFormat,
  checkpointer,
});

// Run agent
// `thread_id` is a unique identifier for a given conversation.
const config = {
  configurable: { thread_id: "1" },
  context: { user_id: "1" },
};

const response = await agent.invoke(
  { messages: [{ role: "user", content: "what is the weather outside?" }] },
  config
);
console.log(response.structuredResponse);
// {
//   punny_response: "Florida is still having a 'sun-derful' day! The sunshine is playing 'ray-dio' hits all day long! I'd say it's the perfect weather for some 'solar-bration'! If you were hoping for rain, I'm afraid that idea is all 'washed up' - the forecast remains 'clear-ly' brilliant!",
//   weather_conditions: "It's always sunny in Florida!"
// }

// Note that we can continue the conversation using the same `thread_id`.
const thankYouResponse = await agent.invoke(
  { messages: [{ role: "user", content: "thank you!" }] },
  config
);
console.log(thankYouResponse.structuredResponse);
// {
//   punny_response: "You're 'thund-erfully' welcome! It's always a 'breeze' to help you stay 'current' with the weather. I'm just 'cloud'-ing around waiting to 'shower' you with more forecasts whenever you need them. Have a 'sun-sational' day in the Florida sunshine!",
//   weather_conditions: undefined
// }