ElleNajt/emacs-introspection-mcp

#+title: Readme

A simple MCP server for emacs introspection through the emacsclient daemon.

This server currently provides three tools for interacting with Emacs:

1. describe_function - Retrieves documentation for Emacs functions
2. describe_variable - Retrieves documentation for Emacs variables
3. get_variable_value - Gets the current value of an Emacs variable

• Warning

All of these evaluate elisp via the emacsclient, though they do so in the following controlled ways:

#+begin_src bash emacsclient -e "(documentation '$FUNCTION_NAME)" emacsclient -e "(documentation-property '$VARIABLE_NAME 'variable-documentation)" emacsclient -e "(symbol-value '$VARIABLE_NAME)" #+end_src

The security measures to prevent weird injections from the LLM are:

• Using ', which in my understanding prevents evaluation of the form following it, unlike backtick (which would be vulnerable to an LLM passing in a , to escape the quoting.)
• Using execFile with shell=false to on the typescript side, to prevent shell injection
• Sanitized with this regexp:

#+begin_src ts const isValidEmacsSymbol = (str: string) => /^[a-zA-Z0-9-_]+$/.test(str); #+end_src

• Installation

First, set up [[https://github.com/karthink/gptel][gptel]] and [[https://github.com/lizqwerscott/mcp.el][mcp.el]] .

Then, add this to your the mcp-hub-servers variable:

#+begin_src emacs-lisp :tangle yes ("emacs_introspection" . (:command "npx" :args ("-y" "@lnajt/emacs-introspection-mcp")) ) #+end_src

• Implementation details

** describe_function Gets the documentation for an Emacs function by name.

• Parameter: function_name (string)
• Implementation: Uses emacsclient to call (documentation 'function-name)

** describe_variable Gets the documentation for an Emacs variable by name.

• Parameter: variable_name (string)
• Implementation: Uses emacsclient to call (documentation-property 'variable-name 'variable-documentation)

** get_variable_value Gets the current value of an Emacs variable by name.

• Parameter: variable_name (string)
• Implementation: Uses emacsclient to call (symbol-value 'variable-name )