elisp-dev-mcp

#+TITLE: elisp-dev-mcp: MCP Server for Agentic Elisp Development

[[https://github.com/laurynas-biveinis/elisp-dev-mcp/actions/workflows/elisp-test.yml][https://github.com/laurynas-biveinis/elisp-dev-mcp/actions/workflows/elisp-test.yml/badge.svg]] [[https://github.com/laurynas-biveinis/elisp-dev-mcp/actions/workflows/super-linter.yml][https://github.com/laurynas-biveinis/elisp-dev-mcp/actions/workflows/super-linter.yml/badge.svg]] [[https://melpa.org/#/elisp-dev-mcp][https://melpa.org/packages/elisp-dev-mcp-badge.svg]] [[https://stable.melpa.org/#/elisp-dev-mcp][file:https://stable.melpa.org/packages/elisp-dev-mcp-badge.svg]]

• Overview

=elisp-dev-mcp= is an Emacs package that provides an MCP (Machine Code Protocol) server for agentic Elisp development. It enables AI agents to assist with Elisp coding tasks by providing a structured API to interact with Emacs and manipulate Elisp code.

This package leverages [[https://github.com/laurynas-biveinis/mcp-server-lib.el][mcp-server-lib.el]] for the underlying MCP infrastructure.

• Installation

From MELPA:

=M-x package-install RET elisp-dev-mcp RET=

• Usage

** Registering with an MCP Client

After =mcp-server-lib= has been properly installed (including =M-x mcp-server-lib-install=), register =elisp-dev-mcp= with your MCP client:

#+begin_example claude mcp add -s user -t stdio elisp-dev -- ~/.emacs.d/emacs-mcp-stdio.sh --init-function=elisp-dev-mcp-enable --stop-function=elisp-dev-mcp-disable --server-id=elisp-dev-mcp #+end_example

Before using the MCP server, you must start it in Emacs with =M-x mcp-server-lib-start=. Stop it with =M-x mcp-server-lib-stop= when done.

** Available MCP Handlers

*** Elisp Function Documentation

• Name: =elisp-describe-function=

• Description: Get full documentation for an Emacs Lisp function

• Parameters:

  • =function=: The name of the function to describe (string)

• Returns:

  • =description=: The function's documentation (string)

  • or =error=: Error message if something went wrong (string)

*** Elisp Function Definition

• Name: =elisp-get-function-definition=

• Description: Get the source code definition of an Emacs Lisp function

• Parameters:

  • =function=: The name of the function to retrieve (string)

• Returns:

  • For Elisp functions:

    • =source=: The function's source code including header comments if present (string)

    • =file-path=: Path to the file where the function is defined (string)

    • =start-line=: First line number of the definition including header comments (1-based integer)

    • =end-line=: Last line number of the definition (1-based integer)

  • For C-implemented functions:

    • =is-c-function=: Boolean indicator that this is a C function (always true)

    • =function-name=: The name of the function (string)

    • =message=: A message indicating the function is implemented in C source code (string)

*** Elisp Variable Description

• Name: =elisp-describe-variable=

• Description: Get information about an Emacs Lisp variable without exposing its value

• Parameters:

  • =variable=: The name of the variable to describe (string)

• Returns:

  • =name=: Variable name (string)

  • =bound=: Whether variable is currently bound (boolean, false for declared but unbound variables)

  • =value-type=: Type of the value (string, e.g. "cons", "string", "integer")

  • =documentation=: Variable documentation or null if none (string or null)

  • =source-file=: Path to the file where the variable is defined (string)

  • =is-custom=: Whether it's a customizable variable (boolean)

  • =custom-group=: The custom group this variable belongs to (string, only present for custom variables)

  • =custom-type=: The custom type specification (string, only present for custom variables)

  • =is-obsolete=: Whether the variable is marked obsolete (boolean)

  • =obsolete-since=: Version when the variable became obsolete (string, only present if obsolete)

  • =obsolete-replacement=: Suggested replacement for the obsolete variable (string, only present if obsolete)

  • =is-alias=: Whether the variable is an alias for another variable (boolean)

  • =alias-target=: The variable this is an alias for (string, only present if alias)

  • =is-special=: Whether the variable is a special (dynamically scoped) variable (boolean)

  • or =error=: Error message if something went wrong (string)

*** Elisp Info Documentation Lookup

• Name: =elisp-info-lookup-symbol=

• Description: Look up Elisp symbols in Info documentation and return the complete documentation node

• Parameters:

  • =symbol=: The Elisp symbol to look up (string)

• Returns:

  • =found=: Whether documentation was found (boolean)

  • =symbol=: The symbol that was looked up (string)

  • =node=: The Info node name containing the documentation (string, when found)

  • =manual=: The Info manual name, typically 'elisp' (string, when found)

  • =content=: The complete Info node content including all examples, cross-references, and related information (string, when found)

  • =info-ref=: Info reference like '(elisp)Node Name' for direct access (string, when found)

  • =message=: Error or not-found message (string, when not found)

*** Elisp Source File Reader

• Name: =elisp-read-source-file=

• Description: Read Elisp source files from Emacs system directories or ELPA packages

• Parameters:

  • =file-path=: Absolute path to =.el= file (string)

• Returns:

  • The complete file contents as a string

  • or =error=: Error message if file not found, invalid format, or access denied (string)

• Examples:

  • ="/opt/homebrew/Cellar/emacs-mac/emacs-29.1-mac-10.0/share/emacs/29.1/lisp/files.el"= - Read system file

  • ="/Users/name/.emacs.d/elpa/package-1.0/package.el"= - Read ELPA package

• Security:

  • Only reads from Emacs system lisp directories and =~/.emacs.d/elpa/=

  • Rejects paths with =..= traversal

  • Resolves symlinks to prevent escaping allowed directories

• Features:

  • Transparently handles =.el.gz= compressed files

  • Works directly with paths from =elisp-get-function-definition=

  • Returns complete file contents as string

• License

This project is licensed under the GNU General Public License v3.0 (GPLv3) - see the LICENSE file for details.