How to integrate Postman MCP with LangChain

This guide walks you through connecting Postman to LangChain using the Composio tool router. By the end, you'll have a working Postman agent that can run the 'get users' request in postman, list all collections in your postman workspace, create a new environment variable in postman through natural language commands. This guide will help you understand how to give your LangChain agent real control over a Postman account through Composio's Postman MCP server. Before we dive in, let's take a quick look at the key ideas and tools involved.

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Introduction

This guide walks you through connecting Postman to LangChain using the Composio tool router. By the end, you'll have a working Postman agent that can run the 'get users' request in postman, list all collections in your postman workspace, create a new environment variable in postman through natural language commands.

This guide will help you understand how to give your LangChain agent real control over a Postman account through Composio's Postman MCP server.

Before we dive in, let's take a quick look at the key ideas and tools involved.

Also integrate Postman with

TL;DR

Here's what you'll learn:
  • Get and set up your OpenAI and Composio API keys
  • Connect your Postman project to Composio
  • Create a Tool Router MCP session for Postman
  • Initialize an MCP client and retrieve Postman tools
  • Build a LangChain agent that can interact with Postman
  • Set up an interactive chat interface for testing

What is LangChain?

LangChain is a framework for developing applications powered by language models. It provides tools and abstractions for building agents that can reason, use tools, and maintain conversation context.

Key features include:

  • Agent Framework: Build agents that can use tools and make decisions
  • MCP Integration: Connect to external services through Model Context Protocol adapters
  • Memory Management: Maintain conversation history across interactions
  • Multi-Provider Support: Works with OpenAI, Anthropic, and other LLM providers

What is the Postman MCP server, and what's possible with it?

The Postman MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Postman account. It provides structured and secure access so your agent can perform Postman operations on your behalf.

What is the Composio tool router, and how does it fit here?

What is Composio SDK?

Composio's Composio SDK helps agents find the right tools for a task at runtime. You can plug in multiple toolkits (like Gmail, HubSpot, and GitHub), and the agent will identify the relevant app and action to complete multi-step workflows. This can reduce token usage and improve the reliability of tool calls. Read more here: Getting started with Composio SDK

The tool router generates a secure MCP URL that your agents can access to perform actions.

How the Composio SDK works

The Composio SDK follows a three-phase workflow:

  1. Discovery: Searches for tools matching your task and returns relevant toolkits with their details.
  2. Authentication: Checks for active connections. If missing, creates an auth config and returns a connection URL via Auth Link.
  3. Execution: Executes the action using the authenticated connection.

Step-by-step Guide

Step by step10 STEPS
1

Prerequisites

Before starting this tutorial, make sure you have:
  • Python 3.10 or higher installed on your system
  • A Composio account with an API key
  • An OpenAI API key
  • Basic familiarity with Python and async programming
2

Getting API Keys for OpenAI and Composio

OpenAI API Key
  • Go to the OpenAI dashboard and create an API key. You'll need credits to use the models, or you can connect to another model provider.
  • Keep the API key safe.
Composio API Key
  • Log in to the Composio dashboard.
  • Navigate to your API settings and generate a new API key.
  • Store this key securely as you'll need it for authentication.
3

Install dependencies

npm install @composio/langchain @langchain/core @langchain/openai @langchain/mcp-adapters dotenv

Install the required packages for LangChain with MCP support.

What's happening:

  • @composio/langchain provides Composio integration for LangChain
  • @langchain/mcp-adapters enables MCP client connections
  • @langchain/core is the core agent framework
  • dotenv/config loads environment variables
4

Set up environment variables

bash
COMPOSIO_API_KEY=your_composio_api_key_here
COMPOSIO_USER_ID=your_composio_user_id_here
OPENAI_API_KEY=your_openai_api_key_here

Create a .env file in your project root.

What's happening:

  • COMPOSIO_API_KEY authenticates your requests to Composio's API
  • COMPOSIO_USER_ID identifies the user for session management
  • OPENAI_API_KEY enables access to OpenAI's language models
5

Import dependencies

import { Composio } from '@composio/core';
import { LangchainProvider } from '@composio/langchain';
import { MultiServerMCPClient } from "@langchain/mcp-adapters";
import { createAgent } from "langchain";
import * as readline from 'readline';
import 'dotenv/config';

dotenv.config();
What's happening:
  • We're importing LangChain's MCP adapter and Composio SDK
  • The dotenv/config import loads environment variables from your .env file
  • This setup prepares the foundation for connecting LangChain with Postman functionality through MCP
6

Initialize Composio client

const composioApiKey = process.env.COMPOSIO_API_KEY;
const userId = process.env.COMPOSIO_USER_ID;

if (!composioApiKey) throw new Error('COMPOSIO_API_KEY is not set');
if (!userId) throw new Error('COMPOSIO_USER_ID is not set');

async function main() {
    const composio = new Composio({
        apiKey: composioApiKey as string,
        provider: new LangchainProvider()
    });
What's happening:
  • We're loading the COMPOSIO_API_KEY from environment variables and validating it exists
  • Creating a Composio instance that will manage our connection to Postman tools
  • Validating that COMPOSIO_USER_ID is also set before proceeding
7

Create a Tool Router session

const session = await composio.create(
    userId as string,
    {
        toolkits: ['postman']
    }
);

const url = session.mcp.url;
What's happening:
  • We're creating a Tool Router session that gives your agent access to Postman tools
  • The create method takes the user ID and specifies which toolkits should be available
  • The returned session.mcp.url is the MCP server URL that your agent will use
  • This approach allows the agent to dynamically load and use Postman tools as needed
8

Configure the agent with the MCP URL

const client = new MultiServerMCPClient({
    "postman-agent": {
        transport: "http",
        url: url,
        headers: {
            "x-api-key": process.env.COMPOSIO_API_KEY
        }
    }
});

const tools = await client.getTools();

const agent = createAgent({ model: "gpt-5", tools });
What's happening:
  • We're creating a MultiServerMCPClient that connects to our Postman MCP server via HTTP
  • The client is configured with a name and the URL from our Tool Router session
  • getTools() retrieves all available Postman tools that the agent can use
  • We're creating a LangChain agent using the GPT-5 model
9

Set up interactive chat interface

let conversationHistory: any[] = [];

console.log("Chat started! Type 'exit' or 'quit' to end the conversation.\n");
console.log("Ask any Postman related question or task to the agent.\n");

const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
    prompt: 'You: '
});

rl.prompt();

rl.on('line', async (userInput: string) => {
    const trimmedInput = userInput.trim();

    if (['exit', 'quit', 'bye'].includes(trimmedInput.toLowerCase())) {
        console.log("\nGoodbye!");
        rl.close();
        process.exit(0);
    }

    if (!trimmedInput) {
        rl.prompt();
        return;
    }

    conversationHistory.push({ role: "user", content: trimmedInput });
    console.log("\nAgent is thinking...\n");

    const response = await agent.invoke({ messages: conversationHistory });
    conversationHistory = response.messages;

    const finalResponse = response.messages[response.messages.length - 1]?.content;
    console.log(`Agent: ${finalResponse}\n`);
        
        rl.prompt();
    });

    rl.on('close', () => {
        console.log('\n👋 Session ended.');
        process.exit(0);
    });
What's happening:
  • We initialize an empty conversationHistory list to maintain context across interactions
  • A readline interface is used to continuously accept user input from the command line
  • When a user types a message, it's added to the conversation history and sent to the agent
  • The agent processes the request using the invoke() method with the full conversation history
  • Users can type 'exit', 'quit', or 'bye' to end the chat session gracefully
10

Run the application

main().catch((err) => {
    console.error('Fatal error:', err);
    process.exit(1);
});
What's happening:
  • We call the main() function to start the application

Complete Code

Here's the complete code to get you started with Postman and LangChain:

import { Composio } from '@composio/core';
import { LangchainProvider } from '@composio/langchain';
import { MultiServerMCPClient } from "@langchain/mcp-adapters";  
import { createAgent } from "langchain";
import * as readline from 'readline';
import 'dotenv/config';

const composioApiKey = process.env.COMPOSIO_API_KEY;
const userId = process.env.COMPOSIO_USER_ID;

if (!composioApiKey) throw new Error('COMPOSIO_API_KEY is not set');
if (!userId) throw new Error('COMPOSIO_USER_ID is not set');

async function main() {
    const composio = new Composio({
        apiKey: composioApiKey as string,
        provider: new LangchainProvider()
    });

    const session = await composio.create(
        userId as string,
        {
            toolkits: ['postman']
        }
    );

    const url = session.mcp.url;
    
    const client = new MultiServerMCPClient({
        "postman-agent": {
            transport: "http",
            url: url,
            headers: {
                "x-api-key": process.env.COMPOSIO_API_KEY
            }
        }
    });
    
    const tools = await client.getTools();
  
    const agent = createAgent({ model: "gpt-5", tools });
    
    let conversationHistory: any[] = [];
    
    console.log("Chat started! Type 'exit' or 'quit' to end the conversation.\n");
    console.log("Ask any Postman related question or task to the agent.\n");
    
    const rl = readline.createInterface({
        input: process.stdin,
        output: process.stdout,
        prompt: 'You: '
    });

    rl.prompt();

    rl.on('line', async (userInput: string) => {
        const trimmedInput = userInput.trim();
        
        if (['exit', 'quit', 'bye'].includes(trimmedInput.toLowerCase())) {
            console.log("\nGoodbye!");
            rl.close();
            process.exit(0);
        }
        
        if (!trimmedInput) {
            rl.prompt();
            return;
        }
        
        conversationHistory.push({ role: "user", content: trimmedInput });
        console.log("\nAgent is thinking...\n");
        
        const response = await agent.invoke({ messages: conversationHistory });
        conversationHistory = response.messages;
        
        const finalResponse = response.messages[response.messages.length - 1]?.content;
        console.log(`Agent: ${finalResponse}\n`);
        
        rl.prompt();
    });

    rl.on('close', () => {
        console.log('\nSession ended.');
        process.exit(0);
    });
}

main().catch((err) => {
    console.error('Fatal error:', err);
    process.exit(1);
});

Conclusion

You've successfully built a LangChain agent that can interact with Postman through Composio's Tool Router.

Key features of this implementation:

  • Dynamic tool loading through Composio's Tool Router
  • Conversation history maintenance for context-aware responses
  • Async Python provides clean, efficient execution of agent workflows
You can extend this further by adding error handling, implementing specific business logic, or integrating additional Composio toolkits to create multi-app workflows.
TOOLS

Supported Tools

Every Postman action and event your agent gets out of the box.

Create a Collection

Tool to create a new Postman collection in a specific workspace or the default workspace.

Create a Collection Comment

Tool to create a comment on an API's collection.

Create Collection from Schema

Tool to create a collection from a schema and link it to an API with specified relations.

Create a Folder

Tool to create a folder in a Postman collection.

Create a Folder Comment

Tool to create a comment on a folder.

Create a Fork

Tool to create a fork from an existing collection into a workspace.

Create Environment Fork

Tool to create a fork from an existing environment into a workspace.

Create a Mock Server

Tool to create a new mock server in a Postman collection.

Create a Monitor

Tool to create a new monitor in a specific workspace to run a collection on a schedule.

Create an API

Tool to create a new API in Postman.

Create an API

Tool to create a new API in a Postman workspace.

Create an Environment

Tool to create a new environment in a Postman workspace.

Create a Pull Request

Tool to create a pull request for a forked collection into its parent collection.

Create Request in Collection

Tool to create a new request in a Postman collection.

Create a Request Comment

Tool to create a comment on a request.

Create a Response

Tool to create a request response in a Postman collection.

Create a Response Comment

Tool to create a comment on a response.

Create API Schema

Tool to create a schema for an API in Postman.

Create Mock Server Response

Tool to create a server response on a Postman mock server.

Create a Spec

Tool to create an API specification in Postman's Spec Hub.

Create Spec File

Tool to create a new file in an API specification.

Create a Webhook

Tool to create a webhook that triggers a collection with a custom payload.

Create a Workspace

Tool to create a new workspace in Postman.

Create Collection

Tool to create a new Postman collection with specified name and configuration.

Create Environment

Tool to create a new Postman environment with specified name and variables.

Create Mock Server

Tool to create a new mock server for a Postman collection.

Create Monitor

Tool to create a new monitor to run a collection on a schedule.

Create or Update a Schema File

Tool to create or update an API schema file in Postman.

Create API Version Relations

Tool to create new relations for an API version.

Create Webhook

Tool to create a new webhook for a Postman collection.

Delete a Collection

Tool to permanently delete a collection from Postman.

Delete a collection's comment

Tool to delete a comment from an API's collection.

Delete a Folder

Tool to delete a folder in a Postman collection.

Delete a Folder's Comment

Tool to delete a comment from a folder.

Delete an API

Tool to delete an API from Postman.

Delete an API's Comment

Tool to delete a comment from an API.

Delete an environment

Tool to delete an environment permanently in Postman.

Delete a Request's Comment

Tool to delete a comment from a request.

Delete a Response

Tool to delete a response in a Postman collection.

Delete a Response's Comment

Tool to delete a comment from a response.

Delete a Schema File

Tool to delete a file in an API schema.

Delete Mock Server Response

Tool to delete a mock server's server response.

Delete a Spec

Tool to delete an API specification from Postman.

Delete Spec File

Tool to delete a file from an API specification.

Delete a Workspace

Tool to delete a Postman workspace permanently.

Delete Monitor

Tool to delete a monitor by its ID.

Duplicate a Collection

Tool to create a duplicate of a collection in another workspace.

Fork Collection

Tool to create a fork of a collection in a specified workspace.

Generate Collection from Spec

Tool to generate a Postman collection from an OpenAPI 2.

Generate Spec from Collection

Tool to generate an API specification from a Postman collection.

Get Billing Account Details

Tool to retrieve Postman billing account details for the authenticated team.

Get Collection Comments

Tool to retrieve all comments left by users in an API's collection.

Get Collection's Forks

Tool to get all forks of a specific collection.

Get Collection Pull Requests

Tool to get information about a collection's pull requests including source and destination IDs, status, and URLs.

Get Collection Roles

Tool to get information about all roles in a collection.

Get Folder Information

Tool to retrieve information about a folder in a Postman collection.

Get Folder Comments

Tool to retrieve all comments left by users in a folder.

Get All API Releases

Tool to get all releases for a specific API version in Postman.

Get All APIs

Tool to get all APIs accessible to the authenticated user with optional workspace filtering.

Get All APIs in Workspace

Tool to get all APIs in a specific Postman workspace.

Get All Collections

Tool to get all collections accessible to the authenticated user with optional workspace filtering.

Get All Collections

Tool to get all collections accessible to the authenticated user.

Get All Environments

Tool to get all environments accessible to the authenticated user with optional workspace filtering.

Get All Forked Collections

Tool to retrieve all forked collections for the authenticated user.

Get All Groups

Tool to get all user groups in a Postman team.

Get All Linked Relations

Tool to retrieve all linked relations for a specific API version in Postman.

Get All Mock Servers

Tool to get all active mock servers accessible to the authenticated user.

Get All Monitors

Tool to get all monitors accessible to the authenticated user with optional workspace filtering.

Get All Workspace Roles

Tool to get information about all roles in a workspace based on the team's plan.

Get All API Specifications

Tool to get all API specifications in a workspace.

Get All Team Users

Tool to get information about all users on the Postman team.

Get All Test Relations

Tool to retrieve all test relations for a specific API version.

Get All API Versions

Tool to get all published versions of a specific API in Postman.

Get All Workspaces

Tool to get all workspaces accessible to the authenticated user with optional type filtering.

Get Monitor Information

Tool to retrieve information about a specific monitor in Postman.

Get API Information

Tool to retrieve information about a specific API in Postman.

Get API Comments

Tool to retrieve all comments left by users in an API.

Get API Version

Tool to get information about a specific API version in Postman.

Get an Environment

Tool to retrieve detailed information about a specific environment in Postman.

Get Environment Forks

Tool to retrieve all forked environments for a specific environment.

Get Request Information

Tool to retrieve information about a specific request in a Postman collection.

Get Request Comments

Tool to retrieve all comments left by users in a request.

Get Response Information

Tool to retrieve information about a saved response in a Postman collection.

Get Response Comments

Tool to retrieve all comments left by users in a response.

Get API Schema

Tool to retrieve information about an API schema from Postman.

Get API Specification

Tool to retrieve information about an API specification in Postman.

Get Spec File Contents

Tool to get the contents of an API specification's file.

Get Spec Definition

Tool to get the complete contents of an API specification's definition.

Get Specification Files

Tool to retrieve all files in an API specification from Postman.

Get Spec's Generated Collections

Tool to retrieve all collections generated from an API specification in Postman.

Get Async Collection Update Status

Tool to get the status of an asynchronous collection update task.

Get Team User

Tool to get information about a user on the Postman team.

Get Authenticated User

Tool to get information about the authenticated user.

Get Workspace Details

Tool to get detailed information about a specific workspace by its ID.

Get Workspace Activity Feed

Tool to get a workspace's activity feed showing who added or removed collections, environments, or elements, and users joining or leaving.

Get Workspace Roles

Tool to get the roles of users, user groups, and partners in a workspace.

Get Collection Access Keys

Tool to retrieve all personal and team collection access keys for the authenticated user.

Get Contract Test Relations

Tool to retrieve contract test relations for a specific API version.

Get documentation relations

Tool to get documentation relations for a specific API version.

Get Duplication Task Status

Tool to get the status of a collection duplication task.

Get Environment Relations

Tool to get environment relations for a specific API version.

Get Generated Specification

Tool to retrieve the API specification generated for a Postman collection.

Get Workspace Global Variables

Tool to get a workspace's global variables.

Get Integration Test Relations

Tool to get integration test relations for a specific API version.

Get Resource Types

Tool to get all resource types supported by Postman's SCIM API.

Get Schema File Contents

Tool to get the contents of an API schema file at a specified path.

Get Schema Files

Tool to retrieve files in an API schema from Postman.

Get Service Provider Configuration

Tool to get Postman's SCIM API service provider configuration information.

Get Source Collection Status

Tool to check whether there is a change between a forked collection and its parent (source) collection.

Get Test Suite Relations

Tool to get test suite relations for a specific API version.

Get Unclassified Relations

Tool to get unclassified relations for an API version in Postman.

Import OpenAPI Definition

Tool to import an OpenAPI definition into Postman as a new collection.

Import OpenAPI Specification

Tool to import an OpenAPI specification into Postman as a new collection.

List Account Invoices

Tool to get all invoices for a Postman billing account filtered by status.

Merge a Fork

Tool to merge a forked collection back into its parent collection.

Merge a forked environment

Tool to merge a forked environment back into its parent environment.

Publish a Mock Server

Tool to publish a mock server in Postman.

Pull Source Changes into Fork

Tool to pull changes from a parent (source) collection into a forked collection.

Replace an Environment's Data

Tool to completely replace an environment's data with new variables and values.

Replace Collection Data Asynchronously

Tool to replace the entire contents of a collection asynchronously.

Resolve a Comment Thread

Tool to resolve a comment thread and any associated replies.

Review a Pull Request

Tool to update the review status of a pull request by approving, declining, or unapproving it.

Run a Monitor

Tool to trigger an immediate run of a monitor and retrieve its execution results.

Sync Collection with API Schema

Tool to sync a collection attached to an API with the API schema.

Sync Collection with Specification

Tool to sync a collection generated from an API specification.

Sync Spec with Collection

Tool to sync an API specification with a linked collection.

Transfer Folders

Tool to copy or move folders into a collection or folder.

Transform Collection to OpenAPI

Tool to transform an existing Postman Collection into a stringified OpenAPI 3.

Update a Folder

Tool to update a folder in a Postman collection.

Update a Folder's Comment

Tool to update a comment on a folder.

Update a Mock Server

Tool to update an existing mock server.

Update a Monitor

Tool to update an existing monitor in Postman.

Update an API

Tool to update an existing API in Postman.

Update an API's Comment

Tool to update a comment on an API.

Update an Environment

Tool to update specific environment properties using JSON Patch operations (RFC 6902).

Update a Pull Request

Tool to update an open pull request in Postman.

Update Request in Collection

Tool to update a request in a Postman collection.

Update a Request's Comment

Tool to update a comment on a request.

Update a Response

Tool to update a response in a Postman collection.

Update a Response's Comment

Tool to update a comment on a response.

Update a Server Response

Tool to update a mock server's server response.

Update Spec File

Tool to update an API specification file's content.

Update Spec Properties

Tool to update an API specification's properties such as its name.

Update a Workspace

Tool to update an existing workspace in Postman.

Update Workspace Global Variables

Tool to update and replace a workspace's global variables.

Update Collection Properties

Tool to update specific collection properties like name, description, authentication, variables, or events.

FAQ

Frequently asked questions

With a standalone Postman MCP server, the agents and LLMs can only access a fixed set of Postman tools tied to that server. However, with the Composio Tool Router, agents can dynamically load tools from Postman and many other apps based on the task at hand, all through a single MCP endpoint.

Yes, you can. LangChain fully supports MCP integration. You get structured tool calling, message history handling, and model orchestration while Tool Router takes care of discovering and serving the right Postman tools.

Yes, absolutely. You can configure which Postman scopes and actions are allowed when connecting your account to Composio. You can also bring your own OAuth credentials or API configuration so you keep full control over what the agent can do.

All sensitive data such as tokens, keys, and configuration is fully encrypted at rest and in transit. Composio is SOC 2 Type 2 compliant and follows strict security practices so your Postman data and credentials are handled as safely as possible.

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