The short answer
What is MCP server, in one line? A program that offers tools and data to an AI assistant through the Model Context Protocol, an open standard Anthropic published in November 2024. The assistant asks what tools exist, calls one, and gets structured results back. Think of it as a manifest plus message passing, for AI.
- MCP is an open protocol for AI tools.
- A server lists tools; a client calls them.
- Local servers talk over stdio; remote ones over HTTP.
- Extension builders already know the pattern.
What is MCP server, if you've written a Chrome extension? You've already done most of the thinking MCP asks for. You declared what your code can do, and parts of it sent messages to each other.
MCP is that, pointed at an AI.
The Model Context Protocol is open, and Anthropic announced it in November 2024.
What is MCP server? Three parts in one picture
There are three parts. The host is the app you type into, like Claude Desktop. Inside it, a client speaks MCP. The server is your program, offering tools.
| MCP piece | Extension cousin | Job |
|---|---|---|
| Server | Background service worker | Does the real work |
| Tool list | Manifest | Declares what's offered |
| Tool call | runtime.sendMessage | Asks for one action |
| Result | Message response | Sends structured data back |
| Host approval | Permission prompt | User says yes or no |
The match isn't perfect. Close, though. It's close enough to get you building in an afternoon.
How a call actually flows
- The client connects and asks the server for its tool list.
- Each tool comes with a name, a description and an input schema.
- The model reads those and decides a tool would help.
- The client sends the call; the server runs it and replies.
The model never touches your database directly. It only sees what your tool returns, which is where you control truth and privacy.
For the current numbers, check the Developer Tools category page.
Local or remote
The spec defines two transports. A local server runs on the user's machine and talks over stdio. A remote server sits behind a URL and uses Streamable HTTP.
Local is easier to start. Remote is what you'd sell, because users don't install anything and you can gate access with a key.
Every guide in this series
This page is the hub for our guides on AI and MCP. Each one goes deeper on a single step:
A first server worth building
Start read-only. A tool that looks things up can't delete anyone's data by accident, and you'll learn the flow without fear.
- One tool that searches your data.
- One tool that fetches a single record.
- Every number returned with the date you observed it.
That last habit stops the model from presenting stale numbers as today's. We're biased, since our own store-data server follows that rule, but the habit holds for any data.
A data server like that answers the questions in Chrome extension market research. For design details, see Chrome Web Store MCP.
Once you've drawn it, MCP stops being a buzzword. It's a manifest and some messages, and you've shipped those before.
Questions people ask
What does an MCP server actually do?
It tells an AI client which tools it offers, accepts calls with arguments, and returns results. The AI decides when to call.
Do you need an MCP server for your Chrome extension?
Only if you want AI assistants to use your data or actions. Most extensions don't need one on day one.
Is MCP only for Claude?
No. It's an open protocol, and other clients such as Cursor support it too.
Where these numbers come from
- anthropic.comAnthropic: Introducing the Model Context Protocol
- modelcontextprotocol.ioModel Context Protocol: introduction
- modelcontextprotocol.ioMCP specification: transports
1,182 new extensions in the last 30 days in Developer Tools. See them all.
Ask Claude about store data directly, or browse the openings yourself. Updated 3 Oct 2026 from our Chrome Web Store crawl
