ToolNode

ToolNode is a prebuilt LangGraph.js runnable that receives an AIMessage with tool calls, looks up the matching tools, executes requested calls—concurrently when there are several—and returns one ToolMessage per call. It accepts graph state containing messages, a message list directly, or tool-call objects, and can be placed in a StateGraph or used independently.

new ToolNode(tools)

A runnable result containing ToolMessages, one for each tool call.

import { AIMessage } from "@langchain/core/messages";
import { tool } from "@langchain/core/tools";
import { ToolNode } from "@langchain/langgraph/prebuilt";

const getWeather = tool(
  async ({ location }: { location: string }) => `Weather in ${location}: sunny`,
  {
    name: "get_weather",
    description: "Get the weather for a location",
    schema: undefined as any
  }
);

const toolNode = new ToolNode([getWeather]);
const message = new AIMessage({
  content: "",
  tool_calls: [{ name: "get_weather", args: { location: "sf" }, id: "call-1", type: "tool_call" }]
});

const result = await toolNode.invoke({ messages: [message] });
console.log(result);

Creates a ToolNode, supplies an AIMessage containing a tool call, and invokes the node to produce the corresponding ToolMessage.