Open Claude Desktop. Ask it: "What's on the Wikipedia article about WebAssembly?"
Without any plugin, it'll guess from training data. With the server I'm about to show you, it'll call a tool named wiki_extract, fetch the real article live, and read it to you. Same client. Same model. Different tools. That switchover is the whole point of the Model Context Protocol.
MCP, released by Anthropic in late 2024, is the open standard that finally answers "how do I give an LLM real-world tools?" Before MCP, every AI app rolled its own plugin system. After MCP, you write a server once and every compatible client speaks to it the same way — Claude Desktop, Cursor, Continue.dev, Zed, custom agents you build with the Anthropic SDK.
Today I'm going to walk you through building one. The whole server is 250 lines. The whole thing.
The mental model
