Basic Agent

We have a comprehensive, step-by-step guide to building agents in LlamaIndex.TS that we recommend to learn what agents are and how to build them for production. But building a basic agent is simple:

Set up

In a new folder:

npm init
npm i -D typescript @types/node
npm i @llamaindex/openai @llamaindex/workflow llamaindex zod

Run agent

Create the file example.ts. This code will:

Create two tools for use by the agent:
- A sumNumbers tool that adds two numbers
- A divideNumbers tool that divides numbers
Give an example of the data structure we wish to generate
Prompt the LLM with instructions and the example, plus a sample transcript

import { openai } from "@llamaindex/openai";
import { agent } from "@llamaindex/workflow";
import { tool } from "llamaindex";
import { z } from "zod";

const sumNumbers = tool({
  name: "sumNumbers",
  description: "Use this function to sum two numbers",
  parameters: z.object({
    a: z.number().describe("The first number"),
    b: z.number().describe("The second number"),
  }),
  execute: ({ a, b }: { a: number; b: number }) => `${a + b}`,
});

const divideNumbers = tool({
  name: "divideNumbers",
  description: "Use this function to divide two numbers",
  parameters: z.object({
    a: z.number().describe("The dividend a to divide"),
    b: z.number().describe("The divisor b to divide by"),
  }),
  execute: ({ a, b }: { a: number; b: number }) => `${a / b}`,
});

async function main() {
  const mathAgent = agent({
    tools: [sumNumbers, divideNumbers],
    llm: openai({ model: "gpt-4.1-mini" }),
    verbose: false,
  });

  const response = await mathAgent.run("How much is 5 + 5? then divide by 2");
  console.log(response.data);
}

void main().then(() => {
  console.log("Done");
});

To run the code:

npx tsx example.ts

You should expect output something like:

{
  result: '5 + 5 is 10. Then, 10 divided by 2 is 5.',
  state: {
    memory: ChatMemoryBuffer {
      chatStore: SimpleChatStore {},
      chatStoreKey: 'chat_history',
      tokenLimit: 750000
    },
    scratchpad: [],
    currentAgentName: 'Agent',
    agents: [ 'Agent' ],
    nextAgentName: null
  }
}
Done

Basic Agent

Set up

Run agent

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