Building Autonomous AI Agents with LangChain.js

LangChain agents can use tools autonomously. Here’s a complete agent setup:

import { ChatOpenAI } from '@langchain/openai';
import { AgentExecutor, createOpenAIToolsAgent } from 'langchain/agents';
import { DynamicTool } from '@langchain/core/tools';
import { ChatPromptTemplate } from '@langchain/core/prompts';

const tools = [
  new DynamicTool({
    name: 'calculator',
    description: 'Performs math calculations',
    func: async (input) => {
      return String(eval(input)); // Use mathjs in production
    }
  }),
  new DynamicTool({
    name: 'search',
    description: 'Search the web',
    func: async (query) => {
      // Your search API here
      return `Results for: ${query}`;
    }
  })
];

const llm = new ChatOpenAI({ model: 'gpt-4' });
const prompt = ChatPromptTemplate.fromMessages([
  ['system', 'You are a helpful assistant with access to tools.'],
  ['human', '{input}'],
  ['placeholder', '{agent_scratchpad}']
]);

const agent = await createOpenAIToolsAgent({ llm, tools, prompt });
const executor = new AgentExecutor({ agent, tools });

const result = await executor.invoke({
  input: 'What is 25 * 48 and search for Node.js news'
});