What is MCP? A plain-English guide

The everyday version

On its own, an assistant only knows what you type or paste into the chat. Ask it about the email the school sent on Tuesday and it has no idea, because it has never seen your inbox.

A connection changes that. Once you connect your mail, the assistant can go and look: find the school's message, read it, and tell you the dates. Connect a calendar and it can check whether Saturday is free. MCP is the common plug that makes these connections work the same way across many assistants and many apps, so each app only has to build its side once.

Who decides what the assistant can do

The app does, not the assistant. When an app offers a connection, it lists exactly which jobs it allows: "search messages", "archive a message", "save a draft". The assistant can only pick from that list. If "send an email" is not on it, there is no way for the assistant to send one, however it is asked.

That is the most useful thing to understand about any connection. The limits that matter live with the app that holds your data.

What you agree to when you connect

• You sign in on the app's own page. The assistant gets a pass for your account, not your password.
• The assistant can use the jobs on the app's list, whenever you ask it to.
• What the assistant reads goes to the company that runs it. If ChatGPT reads an email for you, OpenAI receives that text, the same as if you had pasted it in.
• You can take the pass back, in the app's settings or the assistant's.

Four questions before you connect anything

• What exactly can it do? Look for a plain list.
• Can it do anything you can't undo, like sending, paying or deleting? If yes, does it ask you first?
• Where do you turn it off?
• Are you comfortable with the assistant's company reading what it looks at?

An app that answers all four on one page has thought about it. One that doesn't, probably hasn't.

Where InboxFamily fits

InboxFamily is family email on your own domain, and it offers a connection for your mailbox. Here are our answers to those four questions.

• What it can do: find, read and summarize messages, move them to folders, archive them, mark them read, flagged or spam, and save a draft reply.
• What it can't: send mail or delete it for good. InboxFamily refuses both on its own side, so no assistant can do them, whatever it is asked.
• Turning it off: in your webmail settings, any time. The family admin sees which mailboxes are connected, and children's mailboxes can never be.
• Who reads it: what the assistant looks at goes to the company running it. Your mailbox itself stays with us.

The person who runs the family's domain can also manage mailboxes from chat. For the practical side, see how to manage your email in ChatGPT.

For the curious

MCP stands for Model Context Protocol. Anthropic, the company behind Claude, published it as an open standard in November 2024, and ChatGPT, Claude and a growing list of other assistants now use it.

The app's side is called a server and the assistant's side a client. Each job an app offers is called a tool, and it comes with a short description in plain words, which is how the assistant decides which one fits your request. Tools can also be marked as read-only or as making changes, so a careful assistant knows when to stop and ask you.

Signing in works like the "Sign in with" buttons you already know: you type your password on the app's page, and the assistant receives a pass that can be taken back. No password ever travels through the chat.

The weak spot is the text an assistant reads. A message can carry instructions written for the assistant rather than for you. The guide on MCP email explains what that means for an inbox and how to stay safe.

Read next

• What InboxFamily includes, from storage to assistants.
• Help, for everything about mailboxes and your domain.