How to integrate Brex MCP with LlamaIndex

This guide walks you through connecting Brex to LlamaIndex 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 LlamaIndex 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.

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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 LlamaIndex 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 LlamaIndex 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 ADKLangChainVercel AI SDKMastra AICrewAI

TL;DR

Here's what you'll learn:
  • Set your OpenAI and Composio API keys
  • Install LlamaIndex and Composio packages
  • Create a Composio Tool Router session for Brex
  • Connect LlamaIndex to the Brex MCP server
  • Build a Brex-powered agent using LlamaIndex
  • Interact with Brex through natural language

What is LlamaIndex?

LlamaIndex is a data framework for building LLM applications. It provides tools for connecting LLMs to external data sources and services through agents and tools.

Key features include:

  • ReAct Agent: Reasoning and acting pattern for tool-using agents
  • MCP Tools: Native support for Model Context Protocol
  • Context Management: Maintain conversation context across interactions
  • Async Support: Built for async/await patterns

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 you begin, make sure you have:
  • Python 3.8/Node 16 or higher installed
  • A Composio account with the API key
  • An OpenAI API key
  • A Brex account and project
  • Basic familiarity with async Python/Typescript
2

Getting API Keys for OpenAI, Composio, and Brex

OpenAI API key (OPENAI_API_KEY)
  • Go to the OpenAI dashboard
  • Create an API key if you don't have one
  • Assign it to OPENAI_API_KEY in .env
Composio API key and user ID
  • Log into the Composio dashboard
  • Copy your API key from Settings
    • Use this as COMPOSIO_API_KEY
  • Pick a stable user identifier (email or ID)
    • Use this as COMPOSIO_USER_ID
3

Installing dependencies

npm install @composio/llamaindex @llamaindex/openai @llamaindex/tools @llamaindex/workflow dotenv

Create a new Typescript project and install the necessary dependencies:

  • @composio/llamaindex: Composio's LlamaIndex integration
  • @llamaindex/openai: OpenAI LLM integration
  • @llamaindex/tools: MCP client for LlamaIndex
  • @llamaindex/workflow: Workflow framework for LlamaIndex
  • dotenv: Environment variable management
4

Set environment variables

bash
OPENAI_API_KEY=your-openai-api-key
COMPOSIO_API_KEY=your-composio-api-key
COMPOSIO_USER_ID=your-user-id

Create a .env file in your project root:

These credentials will be used to:

  • Authenticate with OpenAI's GPT-5 model
  • Connect to Composio's Tool Router
  • Identify your Composio user session for Brex access
5

Import modules

import "dotenv/config";
import readline from "node:readline/promises";
import { stdin as input, stdout as output } from "node:process";

import { Composio } from "@composio/core";

import { mcp } from "@llamaindex/tools";
import { agent as createAgent } from "@llamaindex/workflow";
import { openai } from "@llamaindex/openai";

dotenv.config();

Create a new file called brex_llamaindex_agent.ts and import the required modules:

Key imports:

  • dotenv.config loads .env at runtime
  • readline gives us a simple CLI chat loop
  • Composio is the main Composio SDK client
  • mcp connects to an MCP endpoint
  • createAgent builds a LlamaIndex agent
  • openai configures the LLM backend
6

Load environment variables and initialize Composio

const OPENAI_API_KEY = process.env.OPENAI_API_KEY;
const COMPOSIO_API_KEY = process.env.COMPOSIO_API_KEY;
const COMPOSIO_USER_ID = process.env.COMPOSIO_USER_ID;

if (!OPENAI_API_KEY) throw new Error("OPENAI_API_KEY is not set");
if (!COMPOSIO_API_KEY) throw new Error("COMPOSIO_API_KEY is not set");
if (!COMPOSIO_USER_ID) throw new Error("COMPOSIO_USER_ID is not set");

What's happening:

This ensures missing credentials cause early, clear errors before the agent attempts to initialise.

7

Create a Tool Router session and build the agent function

async function buildAgent() {

  console.log(`Initializing Composio client...${COMPOSIO_USER_ID!}...`);
  console.log(`COMPOSIO_USER_ID: ${COMPOSIO_USER_ID!}...`);

  const composio = new Composio({
    apiKey: COMPOSIO_API_KEY,
    provider: new LlamaindexProvider(),
  });

  const session = await composio.create(
    COMPOSIO_USER_ID!,
    {
      toolkits: ["brex"],
    },
  );

  const mcpUrl = session.mcp.url;
  console.log(`Composio Tool Router MCP URL: ${mcpUrl}`);

  const server = mcp({
    url: mcpUrl,
    clientName: "composio_tool_router_with_llamaindex",
    requestInit: {
      headers: {
        "x-api-key": COMPOSIO_API_KEY!,
      },
    },
    // verbose: true,
  });

  const tools = await server.tools();

  const llm = openai({ apiKey: OPENAI_API_KEY, model: "gpt-5" });

  const agent = createAgent({
    name: "composio_tool_router_with_llamaindex",
        description : "An agent that uses Composio Tool Router MCP tools to perform actions.",
    systemPrompt:
      "You are a helpful assistant connected to Composio Tool Router."+
"Use the available tools to answer user queries and perform Brex actions." ,
    llm,
    tools,
  });

  return agent;
}

What's happening here:

  • We create a Composio client using your API key and configure it with the LlamaIndex provider
  • We then create a tool router MCP session for your user, specifying the toolkits we want to use (in this case, brex)
  • The session returns an MCP HTTP endpoint URL that acts as a gateway to all your configured tools
  • LlamaIndex will connect to this endpoint to dynamically discover and use the available Brex tools.
  • The MCP tools are mapped to LlamaIndex-compatible tools and plug them into the Agent.
8

Create an interactive chat loop

async function chatLoop(agent: ReturnType<typeof createAgent>) {
  const rl = readline.createInterface({ input, output });

  console.log("Type 'quit' or 'exit' to stop.");

  while (true) {
    let userInput: string;

    try {
      userInput = (await rl.question("\nYou: ")).trim();
    } catch {
      console.log("\nAgent: Bye!");
      break;
    }

    if (!userInput) {
      continue;
    }

    const lower = userInput.toLowerCase();
    if (lower === "quit" || lower === "exit") {
      console.log("Agent: Bye!");
      break;
    }

    try {
      process.stdout.write("Agent: ");

      const stream = agent.runStream(userInput);
      let finalResult: any = null;

      for await (const event of stream) {
        // The event.data contains the streamed content
        const data: any = event.data;

        // Check for streaming delta content
        if (data?.delta) {
          process.stdout.write(data.delta);
        }

        // Store final result for fallback
        if (data?.result || data?.message) {
          finalResult = data;
        }
      }

      // If no streaming happened, show the final result
      if (finalResult) {
        const answer =
          finalResult.result ??
          finalResult.message?.content ??
          finalResult.message ??
          "";
        if (answer && typeof answer === "string" && !answer.includes("[object")) {
          process.stdout.write(answer);
        }
      }

      console.log(); // New line after streaming completes
    } catch (err: any) {
      console.error("\nAgent error:", err?.message ?? err);
    }
  }

  rl.close();
}

What's happening:

  • We're creating a direct terminal interface to chat with Brex
  • The LLM's responses are streamed to the CLI for faster interaction.
  • The agent uses context to maintain conversation history
  • The agent processes the request, selects appropriate Brex tools, and returns a result
  • We extract the answer from the result data structure and display it to the user
  • You can type 'quit' or 'exit' to stop the chat loop gracefully
  • Agent responses and any errors are streamed in a clear, readable format
9

Define the main entry point

async function main() {
  try {
    const agent = await buildAgent();
    await chatLoop(agent);
  } catch (err) {
    console.error("Failed to start agent:", err);
    process.exit(1);
  }
}

main();

What's happening here:

  • We're orchestrating the entire application flow
  • The agent gets built with proper error handling
  • Then we kick off the interactive chat loop so you can start talking to Brex
10

Run the agent

npx ts-node llamaindex-agent.ts

When prompted, authenticate and authorise your agent with Brex, then start asking questions.

Complete Code

Here's the complete code to get you started with Brex and LlamaIndex:

import "dotenv/config";
import readline from "node:readline/promises";
import { stdin as input, stdout as output } from "node:process";

import { Composio } from "@composio/core";
import { LlamaindexProvider } from "@composio/llamaindex";

import { mcp } from "@llamaindex/tools";
import { agent as createAgent } from "@llamaindex/workflow";
import { openai } from "@llamaindex/openai";

dotenv.config();

const OPENAI_API_KEY = process.env.OPENAI_API_KEY;
const COMPOSIO_API_KEY = process.env.COMPOSIO_API_KEY;
const COMPOSIO_USER_ID = process.env.COMPOSIO_USER_ID;

if (!OPENAI_API_KEY) {
    throw new Error("OPENAI_API_KEY is not set in the environment");
  }
if (!COMPOSIO_API_KEY) {
    throw new Error("COMPOSIO_API_KEY is not set in the environment");
  }
if (!COMPOSIO_USER_ID) {
    throw new Error("COMPOSIO_USER_ID is not set in the environment");
  }

async function buildAgent() {

  console.log(`Initializing Composio client...${COMPOSIO_USER_ID!}...`);
  console.log(`COMPOSIO_USER_ID: ${COMPOSIO_USER_ID!}...`);

  const composio = new Composio({
    apiKey: COMPOSIO_API_KEY,
    provider: new LlamaindexProvider(),
  });

  const session = await composio.create(
    COMPOSIO_USER_ID!,
    {
      toolkits: ["brex"],
    },
  );

  const mcpUrl = session.mcp.url;
  console.log(`Composio Tool Router MCP URL: ${mcpUrl}`);

  const server = mcp({
    url: mcpUrl,
    clientName: "composio_tool_router_with_llamaindex",
    requestInit: {
      headers: {
        "x-api-key": COMPOSIO_API_KEY!,
      },
    },
    // verbose: true,
  });

  const tools = await server.tools();

  const llm = openai({ apiKey: OPENAI_API_KEY, model: "gpt-5" });

  const agent = createAgent({
    name: "composio_tool_router_with_llamaindex",
    description:
      "An agent that uses Composio Tool Router MCP tools to perform actions.",
    systemPrompt:
      "You are a helpful assistant connected to Composio Tool Router."+
"Use the available tools to answer user queries and perform Brex actions." ,
    llm,
    tools,
  });

  return agent;
}

async function chatLoop(agent: ReturnType<typeof createAgent>) {
  const rl = readline.createInterface({ input, output });

  console.log("Type 'quit' or 'exit' to stop.");

  while (true) {
    let userInput: string;

    try {
      userInput = (await rl.question("\nYou: ")).trim();
    } catch {
      console.log("\nAgent: Bye!");
      break;
    }

    if (!userInput) {
      continue;
    }

    const lower = userInput.toLowerCase();
    if (lower === "quit" || lower === "exit") {
      console.log("Agent: Bye!");
      break;
    }

    try {
      process.stdout.write("Agent: ");

      const stream = agent.runStream(userInput);
      let finalResult: any = null;

      for await (const event of stream) {
        // The event.data contains the streamed content
        const data: any = event.data;

        // Check for streaming delta content
        if (data?.delta) {
          process.stdout.write(data.delta);
        }

        // Store final result for fallback
        if (data?.result || data?.message) {
          finalResult = data;
        }
      }

      // If no streaming happened, show the final result
      if (finalResult) {
        const answer =
          finalResult.result ??
          finalResult.message?.content ??
          finalResult.message ??
          "";
        if (answer && typeof answer === "string" && !answer.includes("[object")) {
          process.stdout.write(answer);
        }
      }

      console.log(); // New line after streaming completes
    } catch (err: any) {
      console.error("\nAgent error:", err?.message ?? err);
    }
  }

  rl.close();
}

async function main() {
  try {
    const agent = await buildAgent();
    await chatLoop(agent);
  } catch (err: any) {
    console.error("Failed to start agent:", err?.message ?? err);
    process.exit(1);
  }
}

main();

Conclusion

You've successfully connected Brex to LlamaIndex through Composio's Tool Router MCP layer. Key takeaways:
  • Tool Router dynamically exposes Brex tools through an MCP endpoint
  • LlamaIndex's ReActAgent handles reasoning and orchestration; Composio handles integrations
  • The agent becomes more capable without increasing prompt size
  • Async Python provides clean, efficient execution of agent workflows
You can easily extend this to other toolkits like Gmail, Notion, Stripe, GitHub, and more by adding them to the toolkits parameter.
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

LangChain logo

LangChain

Use Brex MCP with LangChain

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

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. LlamaIndex 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.

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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.

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Co-founder, Opennote

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