MCP lets Claude Code talk to external tools directly. Notion, databases, GitHub, Slack. This guide explains what MCPs are from scratch and walks you through setting up your first one: the Notion MCP.
What Is an MCP?
MCP stands for Model Context Protocol. It's a standard that lets AI models connect to external tools and data sources.
Think of it like a USB port. Your laptop is useful on its own. Plug in a monitor, a drive, a keyboard and it becomes a workstation. MCP does the same thing for Claude. Without MCPs, Claude can only work with what's in your conversation and your local files. With MCPs, Claude can read your Notion workspace, query your database, create GitHub issues, send Slack messages. All from one prompt.
The key thing: Claude doesn't just get data from these tools. It can write back to them. Ask Claude to update a Notion page, and it updates the page.
How MCPs Actually Work
Three components:
MCP Server. A small program that talks to one specific tool. The Notion MCP server reads and writes Notion pages. The Postgres one runs SQL queries. One server per tool.
MCP Client. The AI tool that connects to MCP servers. Claude Code is an MCP client. So is Cursor, Windsurf, and most AI coding tools now.
The Protocol.The standard between them. Defines how the client finds out what the server can do, sends requests, gets responses back. You don't need to understand the protocol to use MCPs. Just know it's the reason any server works with any client.
In practice: you point Claude Code at an MCP server. Claude connects on startup, figures out what tools the server offers, and makes them available. Ask Claude to do something that needs that tool and it calls the server automatically.
What Can You Actually Do With MCPs?
Some real examples:
- Notion MCP. Claude reads and writes your Notion workspace. Search pages, update databases, add new entries.
- Postgres MCP. Claude runs read-only SQL against your database. Ask "how many users signed up this week" and get the real number back.
- GitHub MCP. Create issues, open PRs, read code from repos you don't have cloned locally.
- Slack MCP. Read channels, send messages, pull thread summaries.
There are hundreds of MCP servers. Anthropic maintains official ones for major tools. The community builds the rest.