minimal-mcp
The smallest MCP server that still covers the whole protocol: one file,one todo list, all three primitives, plus elicitation.
uv sync
uv run python smoke_test.py # proves it works -- 12 checks
uv run mcp dev todo_server.py # MCP Inspector -- poke at it in a browser
The one thing to remember
Each MCP primitive is defined by who decides to use it:
| Primitive | Decided by | Here |
|---|---|---|
| Tools | the model | add_todo, complete_todo, remove_todo |
| Resources | the application | todos://all, todos://todo/{id} |
| Prompts | the user | plan_my_day |
remove_todo also demonstrates elicitation — the tool pauses mid-call toask the user "really delete this?" before acting. That's a capability a plainREST endpoint has no way to express.
Why one file
Everything lives in todo_server.py, top to bottom, in the order you'd wantto read it: storage → wire types → server → tools → resources → prompts. Nonavigating between files to see the whole picture.
Storage is a plain in-memory dict — restarting clears it. That's deliberate:this project is about the protocol, not persistence.
Connecting it to a real host
claude mcp add todos -- uv --directory "<absolute path to this repo>" run python todo_server.py
Not yet verified against a real host — only against the Inspector and thesmoke test.
