Setting Up the Brex MCP Server

This guide explains how to connect the official Brex MCP Server to compatible AI clients. The server is hosted by Brex at https://api.brex.com/mcp and supports both OAuth and API key authentication.

Prerequisites

Before any user can connect to the server, an account or card admin must complete two steps in the Brex Dashboard:
Accept the Developer API agreement: Go to Settings → Developer and accept the agreement once.
Enable beta access: Go to Settings → Beta features → Brex in AI Assistants and enable the option.

Once both steps are complete, all users in the company account can connect with their own credentials. Admins do not need to pre-provision tokens for individual users.

Connecting with Claude Code

For Claude Code, a single terminal command is enough:

claude mcp add --transport http brex https://api.brex.com/mcp

You can then verify the connection with claude /mcp. On the first call to a Brex tool, the OAuth flow starts automatically if the client supports OAuth.

If you prefer an API key, pass it as a header:

claude mcp add --transport http brex https://api.brex.com/mcp \
  --header "Authorization: Bearer YOUR_BREX_API_TOKEN"

Connecting with Claude Desktop

Option 1 – Claude Connectors catalog: In Claude Desktop, go to Settings → Connectors, search for "Brex", and install the connector directly.

Option 2 – Manual configuration: Open the config file:
macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
Windows: %APPDATA%\Claude\claude_desktop_config.json

Add the following entry:

{
  "mcpServers": {
    "brex": {
      "command": "npx",
      "args": ["-y", "mcp-remote", "https://api.brex.com/mcp"],
      "env": {}
    }
  }
}

Restart Claude Desktop after saving. Node.js v20 or higher is required.

Connecting with Cursor

In Cursor, open Settings → MCP and add a new server:
Name: brex
Type: http
URL: https://api.brex.com/mcp

Connecting with Codex

codex mcp add brex --url https://api.brex.com/mcp

Connecting with Other MCP Clients

Any client that supports MCP HTTP transport can connect directly to https://api.brex.com/mcp. Clients that support OAuth with Dynamic Client Registration (RFC 7591) receive the authorization flow automatically. For other clients, an API key is required.

Authentication and Token Management

OAuth (recommended): The authorization server is at https://accounts-api.brex.com/oauth2/default. Sessions remain active; repeated login is generally not required. Active connections can be reviewed and revoked under Settings → Personal settings → Connected integrations in the Brex Dashboard.

API key: Create a new token under Settings → Developer with the minimum necessary scopes. Never store the key in repositories, prompts, or shared config files; use the client's secret management features instead. If you suspect a key has been compromised, revoke it immediately and generate a new one.

Security and Best Practices

Enable human confirmation: For tools that can write (memo updates, receipt uploads, limit assignments), enable a confirmation requirement in client settings.
Minimal scopes: When using API keys, grant only the permissions your use case actually requires.
Monitor activity: Check API Logs in the Brex Dashboard regularly to review which tools have been called.
Mind the data path: Tool responses leave Brex and reach the AI client and its model provider. Financially sensitive data (transaction details, expenses, employee data) should never be unnecessarily exposed in prompts or tool calls.

Available Tools at a Glance

After connecting, tools available include: filtering and analyzing expenses, uploading receipts, viewing cards, browsing banking transactions, managing bills and vendors, listing trips and bookings, and accessing accounting records and general ledger accounts. The complete and always-current tool list is in the official documentation at developer.brex.com/docs/mcp.

FAQ

Who needs to activate the MCP Server? An account or card admin must accept the Developer API agreement and enable beta access. After that, all users can connect independently.

Does using the MCP Server cost anything? According to the provider, the MCP Server is available at no extra cost for existing Brex accounts. Any costs depend on the Brex plan, not on MCP access itself.

What happens to my financial data in the AI client? Data returned by the MCP Server is transmitted to the connected client and its model provider. Brex, AI client, and model provider privacy policies all apply simultaneously. Do not embed unnecessary financial data in prompts.

Can I see who used the MCP Server? Yes, the API Logs in the Brex Dashboard allow you to track MCP activity.