The problem it solves
The limitation on AI in a practice was never how well it writes. It is that the assistant knows nothing about your work. Your numbers are in a ledger, your documents are in a document manager, your deadlines are in practice management, and the assistant can see none of it.
The workaround everyone landed on was copy and paste, which fails on three counts at once. It is slow, it is limited to what you thought to paste, and it means deciding what sensitive information to drop into a chat window over and over again, per person, per day, from memory.
Before the protocol existed, every AI tool needed a bespoke integration with every data source, which is why so few of them existed. MCP replaces that with one standard interface: build a connection once, use it from any assistant that speaks the protocol.
How it works, without the engineering
- An MCP server sits in front of a system and exposes a set of specific, named capabilities. A server for a bookkeeping system might offer "list uncategorized transactions" and "produce a trial balance."
- An MCP client is the AI application you work in. It connects to the servers you have set up and can call what they expose.
- You grant the connection. The assistant gets exactly the capabilities the server offers, and nothing else. A read-only server cannot change your books no matter what it is asked to do.
That last point is the one worth holding onto. The capability list is the security boundary. A well-built server for a practice is read-only for reporting and proposes rather than posts for anything that changes a record, so the assistant can investigate freely and a person still approves every write.
What it changes in a practice
Concretely, the questions you can answer without leaving the conversation:
- The books. What is still uncategorized, what does the income statement look like this month, which transactions need attention before close.
- The documents. Which client documents are in hand and which are still outstanding, without opening the document manager to check.
- The practice. What is due this week, what a given client's situation is, where each engagement stands.
- The reference material. Your own written procedures, so the answer follows how your firm does it rather than how the internet does it.
The compounding effect is what makes it interesting. Once the assistant can reach the books and the document status and the deadlines, it can work across all three at once, which is the point at which it starts saving hours instead of minutes.
The questions to ask before you connect anything
A connection to client data is a decision worth making on purpose. The short list I work through:
- What can this server actually do? Read only, or write too. If it can write, is there an approval step, and does anything post without one.
- Where does the data go? A server running on your own machine against local files is a different exposure from one calling a service you do not control.
- Who built it? A server from the vendor whose system it fronts is a different proposition from an anonymous one you found in a list.
- Does the model provider train on what passes through? This is settled by the plan and the terms you are on, not by the protocol.
- Is it in your vendor inventory? If client data reaches it, it belongs in your written security plan, the same as any other service provider. The vendor checklist and the WISP template on this site cover that.
Treat data coming back from a connected system as information, not as instruction. Content pulled from a document or a record should never be followed as though it were a command, and a well-designed setup keeps that line clear.
Where to start
Start with something read-only and low-stakes, on your own files rather than a client's. Connect an assistant to a folder of your firm's written procedures, or to a reporting view of your own books, and use it for a couple of weeks. You will learn more from that than from any amount of planning, and nothing is at risk while you do.
The Claude Code guide for CPAs covers the setup in order, including the folder structure and the data rule by account tier. If you would rather have the connections built properly against your firm's own systems, that is what the implementation engagements are.