LangChain Example

Build agentic workflows with Composio and LangChain/LangGraph

This example demonstrates how to create an autonomous agent using Composio tools with LangChain and LangGraph to build a stateful conversation flow.

Overview

In this example, you’ll learn how to:

• Integrate Composio with LangChain
• Build a state graph for agent workflows
• Create multi-turn conversations with context
• Use tools within a LangGraph workflow

Prerequisites

1. Install dependencies

   npm install @composio/core @composio/langchain @langchain/openai @langchain/core @langchain/langgraph
   
2. Set up environment variables

   Create a .env file with your API keys:

   COMPOSIO_API_KEY=your_composio_api_key
   OPENAI_API_KEY=your_openai_api_key
   

Complete Example

import { ChatOpenAI } from '@langchain/openai';
import { HumanMessage, AIMessage } from '@langchain/core/messages';
import { ToolNode } from '@langchain/langgraph/prebuilt';
import { StateGraph, MessagesAnnotation } from '@langchain/langgraph';
import { Composio } from '@composio/core';
import { LangchainProvider } from '@composio/langchain';

// initiate composio
const composio = new Composio({
  apiKey: process.env.COMPOSIO_API_KEY,
  provider: new LangchainProvider(),
});

// fetch the tool
console.log(`🔄 Fetching the tool...`);
const tools = await composio.tools.get('default', 'HACKERNEWS_GET_USER');

// Define the tools for the agent to use
const toolNode = new ToolNode(tools);

// Create a model and give it access to the tools
const model = new ChatOpenAI({
  model: 'gpt-4o-mini',
  temperature: 0,
}).bindTools(tools);

// Define the function that determines whether to continue or not
function shouldContinue({ messages }: typeof MessagesAnnotation.State) {
  const lastMessage = messages[messages.length - 1] as AIMessage;

  // If the LLM makes a tool call, then we route to the "tools" node
  if (lastMessage.tool_calls?.length) {
    return 'tools';
  }
  // Otherwise, we stop (reply to the user) using the special "__end__" node
  return '__end__';
}

// Define the function that calls the model
async function callModel(state: typeof MessagesAnnotation.State) {
  console.log(`🔄 Calling the model...`);
  const response = await model.invoke(state.messages);

  // We return a list, because this will get added to the existing list
  return { messages: [response] };
}

// Define a new graph
const workflow = new StateGraph(MessagesAnnotation)
  .addNode('agent', callModel)
  .addEdge('__start__', 'agent') // __start__ is a special name for the entrypoint
  .addNode('tools', toolNode)
  .addEdge('tools', 'agent')
  .addConditionalEdges('agent', shouldContinue);

// Finally, we compile it into a LangChain Runnable.
const app = workflow.compile();

// Use the agent
const finalState = await app.invoke({
  messages: [new HumanMessage('Find the details of the user `pg` on HackerNews')],
});
console.log(`✅ Message recieved from the model`);
console.log(finalState.messages[finalState.messages.length - 1].content);

const nextState = await app.invoke({
  // Including the messages from the previous run gives the LLM context.
  // This way it knows we're asking about the weather in NY
  messages: [...finalState.messages, new HumanMessage('what about haxzie')],
});
console.log(`✅ Message recieved from the model`);
console.log(nextState.messages[nextState.messages.length - 1].content);

How It Works

1. Initialize with LangChain Provider

   We initialize Composio with the LangchainProvider, which automatically formats tools for LangChain compatibility.

2. Create Tool Node

   We create a ToolNode from the Composio tools. This node will be responsible for executing tools in the graph.

3. Bind Tools to Model

   We create a ChatOpenAI model and bind the tools to it using .bindTools(). This enables the model to call these tools.

4. Define State Graph

   We create a StateGraph with two nodes:

   • agent: Calls the model to decide the next action
   • tools: Executes the tools when the model requests them
5. Add Conditional Edges

   We add conditional routing logic:

   • If the model makes tool calls → route to tools node
   • Otherwise → end the workflow
6. Execute Workflow

   We invoke the compiled workflow with messages. The graph automatically handles tool execution and maintains conversation state.

Graph Visualization

The workflow graph looks like this:

Expected Output

🔄 Fetching the tool...
🔄 Calling the model...
✅ Message recieved from the model
The user 'pg' on HackerNews is Paul Graham, co-founder of Y Combinator. He has:
- User ID: pg
- Karma: 155,000+
- Account created: February 2007
- Bio: Founder of Y Combinator...

🔄 Calling the model...
✅ Message recieved from the model
The user 'haxzie' on HackerNews has:
- User ID: haxzie
- Karma: 1,234
- Account created: ...

Key Features

Stateful Conversations

LangGraph maintains conversation state across multiple turns. The second query about “haxzie” uses context from the previous conversation.

Automatic Tool Routing

The graph automatically decides when to use tools based on the model’s output, creating an autonomous agent workflow.

Composable Workflows

You can extend this graph with additional nodes for more complex workflows like error handling, validation, or multi-step reasoning.

Advanced Usage

You can extend this example with:

• Streaming: Add streaming support for real-time responses
• Checkpointing: Save and restore conversation state
• Multiple Tools: Add more Composio tools for richer capabilities
• Custom Nodes: Add validation or preprocessing nodes

Next Steps

Custom Tools

Create your own tools with custom logic

OpenAI Example

Learn the basics with OpenAI