How to Connect Brex to Claude (and What It Can't Do)
Brex didn’t wait for the community — it built the MCP server itself. The official Brex MCP server lives at api.brex.com/mcp, authenticates over OAuth (or an API key for programmatic use), and Brex is listed in Claude’s connector directory. It’s labeled beta as of mid-2026, so the tool list is still moving, but this is one of the more legitimate finance integrations you can give Claude: no third-party code to vet, and access mirrors your existing Brex role, so Claude can only see what you’re already allowed to see.
What follows: what the server exposes, what Brex deliberately left out, and why your month-end close still won’t run from a chat window.
What Brex’s server lets Claude see and touch
The design is read-heavy with a few careful writes. On expenses, Claude can view and filter, update memos, upload receipts, manage attendees, and assign spend limits. Beyond that it can read card details, business-account balances and transactions, bills and vendors, travel trips and bookings, team structure, even rewards balances.
Deliberately absent: expense approvals and card management. Claude can’t approve a report, issue a card, or freeze one. Brex drew the line at the actions that move money or credentials, which is the right line.
Prompts a finance person would actually run:
- “Show me every card expense over $500 this month that’s still missing a receipt.”
- “What did we spend on travel in Q2, split by department?”
- “Which spend limits are past 80% with a week left in the month?”
Turning it on
Two routes. From Claude’s connector directory, find Brex and connect — you’ll do a browser OAuth into your Brex account, and the session persists. Or add https://api.brex.com/mcp manually as a custom connector under Settings → Connectors. Both paths need a paid Claude plan. Since the server is in beta, expect occasional tool changes; Brex’s MCP docs track the current surface.
Month-end doesn’t prompt itself
Here’s the structural catch, and it has nothing to do with Brex’s engineering: a Claude connector acts only while you’re in a conversation with it. Nothing watches your account in between.
That maps badly onto how spend management actually works. Receipt chasing is the classic case — your policy gives cardholders a deadline, and Claude can produce a flawless list of offenders when you ask, but it will never nudge anyone on Tuesday morning unprompted. A $4,000 transaction posting at 9 p.m. Friday stays invisible until someone opens a chat. A spend limit blowing past 100% mid-month generates no alert. And since approvals aren’t exposed at all, nothing in this integration moves an expense through review — with or without you present.
Carly handles the recurring finance chores
Carly is an AI executive assistant that works from triggers and schedules rather than prompts, running in the cloud whether your laptop is open or not. The Brex workflows people set up look like: every Monday, pull the missing-receipt list and email each cardholder individually — real sent emails from your Gmail or Outlook, not drafts. When a transaction over a threshold posts, ping the budget owner on Slack and log it. At month-end, assemble the spend summary and file it where the close checklist expects it.
You describe the routine in plain English — “email anyone with a receipt older than seven days outstanding” — and Carly interviews you about the edge cases, then builds the workflow with you. AI agents start at $35/month, and steps that don’t use AI run free and unlimited. See the Brex integration page and the full integrations list.
Brex’s MCP in Claude vs Carly on triggers
| Claude + Brex MCP | Carly | |
|---|---|---|
| Query expenses, transactions, spend limits | Yes — official server | Yes |
| Update memos, attach receipts | Yes, in chat | Yes, in workflows |
| Chase missing receipts on a schedule | No | Yes — recurring, per cardholder |
| Flag a large transaction the moment it posts | No | Yes |
| Escalate to the right approver automatically | No | Yes (email/Slack) |
| Run with your laptop closed | No | Yes — cloud, 24/7 |
| Pricing | Paid Claude plan (server is part of Brex) | AI agents from $35/mo |
Frequently Asked Questions
Does Claude integrate with Brex?
Yes — through Brex’s own official MCP server (api.brex.com/mcp, beta as of mid-2026), which is also listed in Claude’s connector directory. Connect via OAuth on a paid Claude plan and Claude can read expenses, transactions, cards, bills, and travel, with access matching your Brex role.
Can Claude approve Brex expenses?
No. Approvals and card management are intentionally not exposed through Brex’s MCP server. Claude can read and annotate expense data — memos, receipts, attendees — but can’t move anything through review or touch cards.
Can Claude alert me when a big transaction posts?
No. The connector has no triggers; it responds only inside an open chat. For post-time alerts, receipt chasing, and month-end routines that fire on their own, use a trigger-based agent like Carly.
Do I need a paid Claude plan for the Brex connector?
Yes — connectors, including directory ones, require a paid Claude plan. The Brex MCP server itself comes with your Brex account; permissions follow the capabilities your role already has.
What Brex routines can Carly run unattended?
Weekly missing-receipt nudges to each cardholder, instant large-transaction alerts, budget-threshold warnings, and month-end spend summaries — all triggered automatically and delivered by email or Slack. AI agents start at $35/month.
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