Connecting Claude or ChatGPT to your books with MCP

Comma exposes its business-accounting surface as a remote Model Context Protocol (MCP) server. Connect Claude, ChatGPT in developer mode, or Claude Code, and the assistant can read reports, categorize transactions, draft invoices, and reconcile the bank feed — by calling well-defined tools, not by scraping a screen.

Scoped, logged, revocable#

Three properties do the work here:

• Scoped. An assistant never gets more access than the person who connected it. Every tool call is checked against that user's current role on each request, so changing a role or removing someone applies to the very next action — not eventually, and not after a reconnect.
• Logged. Every action lands in your audit trail, tagged as assistant activity rather than blended in with your own.
• Revocable. You can revoke a connection in one click from Settings › Connections. Active sessions stop working immediately.

Connecting always shows an explicit consent screen naming what's being requested and which company it applies to. There is no silent grant — a signed-in user still has to authorize.

Why it's different from copy-paste#

The common way people use an AI assistant with their books today is to paste numbers into a chat window. That has three problems: the assistant sees a snapshot rather than the ledger, nothing it suggests is written back, and there is no record of what it looked at.

Working through MCP inverts all three. The assistant operates through a controlled interface with real permissions and a full audit trail, so it's working with the actual ledger — not a pile of pasted numbers. And because the ledger is immutable, nothing it does can silently rewrite history: corrections are still reversals, whoever posts them.

What you can do with it#

Once connected, useful requests look like ordinary sentences:

• "What did we spend on contractors last quarter?"
• "Categorize the unreviewed bank transactions and tell me which ones you weren't sure about."
• "Draft an invoice to Northwind for the March retainer, but don't send it."

Each of those becomes one or more tool calls against your books, subject to your role, and each one shows up in the audit trail afterwards. You can start free and connect an assistant in a couple of minutes.