Class ToolNode<StateSchema, ContextSchema>

Example

import { ToolNode, tool, AIMessage } from "langchain";
import { z } from "zod/v3";

const getWeather = tool((input) => {
  if (["sf", "san francisco"].includes(input.location.toLowerCase())) {
    return "It's 60 degrees and foggy.";
  } else {
    return "It's 90 degrees and sunny.";
  }
}, {
  name: "get_weather",
  description: "Call to get the current weather.",
  schema: z.object({
    location: z.string().describe("Location to get the weather for."),
  }),
});

const tools = [getWeather];
const toolNode = new ToolNode(tools);

const messageWithSingleToolCall = new AIMessage({
  content: "",
  tool_calls: [
    {
      name: "get_weather",
      args: { location: "sf" },
      id: "tool_call_id",
      type: "tool_call",
    }
  ]
})

await toolNode.invoke({ messages: [messageWithSingleToolCall] });
// Returns tool invocation responses as:
// { messages: ToolMessage[] }
Copy