mcp-python-conventionslisted

# MCP server code conventions The Python inside a stdio-transport MCP server. Split out of `python-conventions` on 2026-08-31, which keeps the general design defaults — this skill owns only what is different _because_ the code is an MCP server, and those differences are not stylistic: two of the three are protocol correctness. Not about shipping. Entry points, `uv tool install`, `claude mcp add` and scope selection belong to `mcp-server-shipping`; this is what the code does once it runs. ## MCP-stdio logging discipline _Scope: stdio-transport MCP servers only (the `*-polite-mcp` family) — not applicable to a repo that has no MCP server of its own._ - Snippet: [`references/snippets/mcp-tool-boundary.py`](references/snippets/mcp-tool-boundary.py) - Default: never a bare `print()` in server package code. Route all logging through the stdlib `logging` module, explicitly configured to write to stderr at startup (or defer to FastMCP's own `configure_logging()`, which already defaults there). - Why: the MCP stdio spec is unambiguous — a server **MUST NOT** write anything to stdout that isn't a valid MCP message; a single stray `print()` or a dependency's stdout-bound log handler corrupts the JSON-RPC stream. stderr is the sanctioned outlet for everything, logs included. - **Don't**: trust that "no `print()` in my code" is sufficient — a dependency that logs to stdout on its own initiative isn't caught by explicit stderr configuration of your own logging. The robust