MCP Has Six Primitives, Not Three. Here's the Half You're Ignoring.
· 12 min read
Pop quiz. Name the MCP primitives.
If you've read any MCP introduction in the last eighteen months, you said: Tools, Resources, Prompts. You're right. Those are the things you build, the things you expose, the things every tutorial walks you through.
You are also wrong, in the sense that you are halfway right.
MCP has six primitives. The three you know are server-side: things your server exposes to the client. The three nobody seems to want to talk about are client-side: things the client exposes to your server. They are Roots, Sampling, and Elicitation, and the reason they get ignored is exactly the reason you should care about them.