PEP Server

MCP server that exposes on-demand Python PEP lookup tools backed by the live PEP index.

Features

• list_peps: list only active PEPs
• search_peps: search active PEP titles
• get_pep: fetch a PEP document by number, optionally returning focused excerpts for a query

Data Sources

• PEP index JSON: https://peps.python.org/api/peps.json
• PEP content:
  • https://raw.githubusercontent.com/python/peps/main/peps/pep-XXXX.rst
  • Fallback: https://github.com/python/peps/blob/main/peps/pep-XXXX.rst?plain=1

Setup

python -m venv .venv
.venv/bin/pip install -e ".[dev]"

Run

.venv/bin/pep-mcp-server

or:

.venv/bin/python -m pep_mcp_server

Docker

Build and tag:

docker build -t pep-mcp-server:latest .

MCP uses stdio, so the container must keep stdin open (-i). Example:

docker run --rm -i pep-mcp-server:latest

Cursor MCP (Docker)

You do not put PEP or GitHub URLs in mcp.json. Cursor only needs the command that runs the server; listing and fetching PEPs happens inside the process when tools run.

Use -i (required for stdio). Optional -e lines silence the startup banner and pin transport:

{
  "mcpServers": {
    "pep": {
      "command": "docker",
      "args": [
        "run",
        "--rm",
        "-i",
        "-e",
        "FASTMCP_TRANSPORT=stdio",
        "-e",
        "FASTMCP_SHOW_SERVER_BANNER=false",
        "pep-mcp-server:latest"
      ]
    }
  }
}

If the image is not on this machine yet, build it once from the project directory (see above).

If the MCP log shows Found 0 tools but listOfferingsForUI / Not connected warnings, that is often a Cursor UI race or a separate UI listing path; try reloading the window or invoking a tool from chat. The server still exposes three tools over stdio (verified with the MCP Python client).

Tool Contracts

list_peps() -> list[dict]

Returns active PEPs with:

• number
• title
• type
• topic
• created
• url

(status is omitted; every row is active.)

search_peps(query: str) -> list[dict]

Case-insensitive substring search on active PEP titles.

get_pep(pep, query=None, max_full_content_chars=None) -> dict

• Accepts 8, 0008, or pep-0008.
• Returns metadata and:
  • content when query is not provided (capped by default for token efficiency)
  • excerpt when query is provided and matches
  • content fallback when query has no matches (also capped by default)
• Optional max_full_content_chars: omit or None for the default cap; use 0 for the full document (can be very large).

Tests

.venv/bin/pytest -q