How to integrate Brex MCP with LangChain

This guide walks you through connecting Brex to LangChain using the Composio tool router. By the end, you'll have a working Brex agent that can create a new card for our intern, get the latest account statement pdf, add an expense for last week's conference through natural language commands. This guide will help you understand how to give your LangChain agent real control over a Brex account through Composio's Brex MCP server. Before we dive in, let's take a quick look at the key ideas and tools involved.

Get started for freeGet a demo
Brex logoBrex
Oauth2Api Key

Brex provides corporate credit cards and spend management tailored for startups and tech businesses. It helps optimize company cash flow, streamline accounting, and accelerate business growth.

84 Tools

Introduction

This guide walks you through connecting Brex to LangChain using the Composio tool router. By the end, you'll have a working Brex agent that can create a new card for our intern, get the latest account statement pdf, add an expense for last week's conference through natural language commands.

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

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

Also integrate Brex with

OpenAI Agents SDKClaude Agent SDKClaude CodeClaude CoworkCodexOpenClawHermesCLIGoogle ADKVercel AI SDKMastra AILlamaIndexCrewAI

TL;DR

Here's what you'll learn:
  • Get and set up your OpenAI and Composio API keys
  • Connect your Brex project to Composio
  • Create a Tool Router MCP session for Brex
  • Initialize an MCP client and retrieve Brex tools
  • Build a LangChain agent that can interact with Brex
  • 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 Brex MCP server, and what's possible with it?

The Brex MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Brex account. It provides structured and secure access to your company's financial tools, so your agent can perform actions like managing cards, tracking expenses, creating budgets, and retrieving account details on your behalf.

  • Card creation and management: Instantly issue new cards, assign them to users or vendors, and control spending limits via your agent.
  • Automated expense tracking: Let your agent create and log expenses, helping you keep company finances organized and up to date.
  • Budget and department setup: Quickly create budgets for teams or projects and set up new departments without manual effort.
  • Account and statement retrieval: Fetch detailed account information and download statements whenever you need financial insights or records.
  • User and location management: Add new users or locations to your Brex account, making it easy to scale as your business grows.

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 Brex 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 Brex 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: ['brex']
    }
);

const url = session.mcp.url;
What's happening:
  • We're creating a Tool Router session that gives your agent access to Brex 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 Brex tools as needed
8

Configure the agent with the MCP URL

const client = new MultiServerMCPClient({
    "brex-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 Brex MCP server via HTTP
  • The client is configured with a name and the URL from our Tool Router session
  • getTools() retrieves all available Brex 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 Brex 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 Brex 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: ['brex']
        }
    );

    const url = session.mcp.url;
    
    const client = new MultiServerMCPClient({
        "brex-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 Brex 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 Brex 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 Brex action and event your agent gets out of the box.

Add Webhook Group Members

Add webhook subscription members to a webhook group.

Archive Budget

Archive a budget to mark it as inactive and prevent future expenses.

Archive Spend Limit

Archive a spend limit in Brex.

Create Budget

Create a new budget for departments or projects.

Create Spend Limit (Budget V1)

Tool to create a new Spend Limit (Budget) in Brex.

Create Card

Create a new card and assign it to a user.

Create Department

Create a new department.

Create Document Upload for Referral

Create a document upload URL for a referral and return a pre-signed S3 upload URL.

Create Expense

Create a new expense.

Create Custom Field

Create a new custom field in Brex.

Create Field Values

Create custom field values for a specific Brex field.

Create Location

Create a new location.

Create Referral Request

Tool to create a new referral to Brex for onboarding.

Create Spend Limit

Tool to create a spend limit in Brex.

Create Job Title

Create a new job title.

Create User

Create a new user in the Brex account.

Create Vendor

Create a new vendor in Brex for payment operations.

Create Webhook Group

Tool to create a webhook group for targeting webhook subscriptions.

Create Webhook Subscription

Register a new webhook subscription to receive real-time notifications for Brex events.

Delete Field

Tool to delete a custom field by Brex ID.

Delete Field Values

Delete custom field values for a specific field.

Delete Vendor

Delete a vendor by ID.

Get Account Statements

Get finalized statements for the primary cash account.

Get Budget Details

Get detailed information about a specific budget.

Get Card Details

Get detailed information about a specific card.

Get Card Expense

Tool to retrieve detailed information about a specific card expense by its ID.

Get Card Number

Get card number, CVV, and expiration date for a specific card.

Get Card Transactions

Get settled card transactions for the primary card account.

Get Company Cash Accounts

Retrieve all cash (deposit) accounts for the company.

Get Company Details

Get company information associated with the OAuth2 access token.

Get Department By ID

Get detailed information about a specific department by ID.

Get Expense

Tool to get details of a specific expense by ID.

Get Field By ID

Tool to retrieve a custom field by its Brex ID.

Get Field Value By ID

Tool to retrieve a specific field value by field ID and field value ID.

Get Legal Entity

Tool to retrieve a legal entity by its ID from Brex.

Get Location By ID

Get detailed information about a specific location by ID.

Get Referral By ID

Tool to retrieve a specific referral by its ID from Brex.

Get Spend Limit By ID

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

Get Spend Limits

Get spend limits configuration.

Get Title by ID

Get detailed information about a specific job title by ID.

Get Transaction by ID

Get details of a specific transaction by ID.

Get Card Transactions

Get card transactions from the primary Brex account.

Get Transactions by Amount Range

Get card transactions filtered by amount range and date period.

Search Transactions by Description

Search and filter card transactions by description text.

Get User Limit

Retrieves the monthly spending limit and available balance for a specific Brex user.

Get User Profile

Get user profile information from Brex Team API.

Get Vendor By ID

Tool to get vendor details by ID.

Get Webhook Group

Tool to retrieve details of a specific webhook group by ID.

Get Webhook Subscription

Tool to retrieve details of a specific webhook subscription by ID.

List Budget Programs

Tool to list all budget programs in the organization.

List Budgets

List all budgets and show available amounts across all cards.

List Card Accounts

Tool to list all card accounts for the company.

List Cards

List all cards associated with the account.

List Card Statements

Tool to list finalized statements for primary card accounts.

List Departments

List all departments in the organization.

List Expenses

Tool to list expenses from the Brex platform.

List Field Values

Tool to list values under a custom field.

List Legal Entities

Tool to list all legal entities in the Brex account with pagination support.

List Locations

List all locations in the organization.

List Referrals

Tool to list all referrals created in the Brex account.

List Job Titles

List all job titles in the organization.

List Transfers

Lists transfers for the account.

List Trips

Lists trips according to the filters passed in the query string.

List Users

List all users in the Brex account.

List Vendors

List all vendors.

List Webhook Group Members

Tool to list all members of a webhook group.

List Webhook Groups

Tool to list all webhook groups.

List Webhook Secrets

Tool to retrieve webhook signing secrets for validating incoming webhook messages from Brex.

List Webhook Subscriptions

Tool to list all registered webhook subscriptions.

Create Receipt Match

Creates a receipt match request and returns a pre-signed S3 upload URI.

Create Receipt Upload for Expense

Creates a receipt upload request for a specific card expense and returns a pre-signed S3 upload URL.

Set User Limit

Set or update the monthly spending limit for a Brex user.

Transfer Card

Transfer a card to a different user.

Update Budget

Update an existing budget's configuration in Brex.

Update Spend Limit (V1)

Tool to update a Spend Limit (budget) using the v1 API.

Update Card Limits

Update spending limits and controls for a Brex card.

Update Card Status

Update the status of a Brex card by locking, unlocking, or terminating it.

Update Expense

Tool to update an expense by its ID.

Update Field

Tool to update a custom field in Brex.

Update Field Values

Tool to update custom field values in Brex for a specific field.

Update Spend Limit

Updates an existing Brex spend limit by its ID.

Update User

Update user details.

Update Vendor

Tool to update vendor information in Brex.

Update Webhook Subscription

Updates an existing Brex webhook subscription's configuration.

FRAMEWORKS

How to build Brex MCP Agent with another framework

OpenAI Agents SDK logo

OpenAI Agents SDK

Use Brex MCP with OpenAI Agents SDK

Claude Agent SDK logo

Claude Agent SDK

Use Brex MCP with Claude Agent SDK

Claude Code logo

Claude Code

Use Brex MCP with Claude Code

Claude Cowork logo

Claude Cowork

Use Brex MCP with Claude Cowork

Codex logo

Codex

Use Brex MCP with Codex

OpenClaw logo

OpenClaw

Use Brex MCP with OpenClaw

Hermes logo

Hermes

Use Brex MCP with Hermes

CLI logo

CLI

Use Brex MCP with CLI

Google ADK logo

Google ADK

Use Brex MCP with Google ADK

Vercel AI SDK logo

Vercel AI SDK

Use Brex MCP with Vercel AI SDK

Mastra AI logo

Mastra AI

Use Brex MCP with Mastra AI

LlamaIndex logo

LlamaIndex

Use Brex MCP with LlamaIndex

CrewAI logo

CrewAI

Use Brex MCP with CrewAI

FAQ

Frequently asked questions

With a standalone Brex MCP server, the agents and LLMs can only access a fixed set of Brex tools tied to that server. However, with the Composio Tool Router, agents can dynamically load tools from Brex 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 Brex tools.

Yes, absolutely. You can configure which Brex 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 Brex data and credentials are handled as safely as possible.

Start with Brex.It takes 30 seconds.

Managed auth, hosted MCP servers, and every Brex tool your agent needs.Free to start.

Start building
Customer stories

Teams ship real agents on Composio

GET STARTED FOR FREEBOOK A DEMO
agent.aiZoomLettaGleanHubSpotAWSWabi

Karan skipped his own birthday party to fix our critical issue. It was 10pm and he diverted his Waymo to help us instead. This really sets the bar — it shows the commitment you need when users rely on your software.

Harsha Gaddipati
Harsha Gaddipati
Co-founder, Slashy

A lot of students tell us that the moment their connected tools start talking to each other inside Opennote feels almost magical. The agent just knows them, and it's immensely helped keep new users on the platform.

Abhi Arya
Abhi Arya
Co-founder, Opennote

We chose Composio over Pipedream because it delivered depth where it mattered — niche tools and tricky edge cases other platforms simply ignored. That gave us confidence to scale without compromising.

Nirman Dave
Nirman Dave
CEO, Zams

As a solo builder, shipping fast is life or death. The only way I can outcompete incumbents is by outmanoeuvring them. Getting bogged down managing agent auth would have been a death sentence.

Ryan Yu
Ryan Yu
Founder, Extra Thursday

Before Composio, adding tool integrations was slow and resource-intensive. Each one could take weeks of engineering time, and maintaining them meant constantly keeping up with API changes.

Tomisin Jenrola
Tomisin Jenrola
Founder & CEO, SwarmZero

With hands-on help from their founder, we integrated Gmail and Google Drive in just 30 minutes. This level of personal support and commitment is exactly what startups should strive for.

Jerome Leclanche
Jerome Leclanche
Co-Founder, Ingram Technologies
Brex MCP Integration with LangChain | Composio