Emacs MCP Plugin

An Osaurus plugin that enables executing Emacs Lisp code in a running Emacs instance via emacsclient.

Based on emacs-mcp-server.

Prerequisites

• Emacs with server mode enabled (M-x server-start or add (server-start) to your init file)
• emacsclient available (auto-detected or specify path)

Tools

execute_emacs_lisp_code

Execute Emacs Lisp code in a running Emacs instance.

Parameters:

• code (required): The Emacs Lisp code to execute
• emacsclient_path (optional): Path to emacsclient binary. Auto-detected if not provided.

Example:

{
  "code": "(buffer-name)",
  "emacsclient_path": "/opt/homebrew/bin/emacsclient"
}

Development

1. Build:

   swift build -c release
   cp .build/release/libEmacs.dylib ./libEmacs.dylib

2. Sign the dylib (required for distributed plugins):

   codesign -s "Developer ID Application: Your Name (TEAMID)" ./libEmacs.dylib

   Note: For local development/testing, you can skip signing. It's only required when distributing the plugin.

3. Install:

   osaurus tools install .

Publishing

This repository includes a portable GitHub Actions workflow that automatically builds, signs, and releases your plugin.

Using This Workflow for Your Own Plugin

The workflow at .github/workflows/release.yml is designed to be easily reusable. To use it for your own Osaurus plugin:

1. Copy the workflow file to your repository
2. Update the configuration section at the top:

env:
  PLUGIN_ID: your.plugin.id
  PLUGIN_NAME: Your Plugin # Display name
  PLUGIN_DESCRIPTION: What it does
  DYLIB_NAME: YourLibrary # Without lib prefix and .dylib extension
  LICENSE: MIT
  MIN_MACOS: "13.0"
  MIN_OSAURUS: "0.5.0"
  TOOLS: '[{"name": "tool_name", "description": "Tool description"}]'

Setup (One-time)

1. Generate a Minisign Key Pair

brew install minisign
minisign -G -p minisign.pub -s minisign.key

This creates:

• minisign.pub - Public key (share this)
• minisign.key - Private key (keep secret!)

2. Export Your Apple Developer Certificate

To code sign the dylib for distribution, you need a Developer ID Application certificate:

1. Open Keychain Access on your Mac
2. Find your "Developer ID Application" certificate
3. Right-click → Export → Save as .p12 with a password
4. Base64 encode it:

   base64 -i certificate.p12 | pbcopy

3. Add Repository Secrets

Go to Settings → Secrets and variables → Actions → Secrets and add:

Secret	Value
MINISIGN_SECRET_KEY	Contents of minisign.key (the entire private key file)
MINISIGN_PUBLIC_KEY	Public key string (second line of .pub file, starts with RW...)
MINISIGN_PASSWORD	Password you set when generating the key (leave empty if none)
DEVELOPER_ID_CERTIFICATE_P12_BASE64	Base64-encoded .p12 certificate (from step 2)
DEVELOPER_ID_CERTIFICATE_PASSWORD	Password you set when exporting the certificate

Creating a Release

Tag and push a version:

git tag 1.0.0
git push origin 1.0.0

The workflow will automatically:

• ✅ Build the plugin for macOS arm64
• ✅ Code sign the dylib (if certificate secrets are configured)
• ✅ Sign artifact with minisign
• ✅ Create a GitHub Release with artifacts
• ✅ Generate the registry entry JSON in release/ folder

Submitting to the Registry

After the workflow completes, you'll find the registry entry at release/<plugin-id>.json. To submit:

1. Fork dinoki-ai/osaurus-tools
2. Copy release/<plugin-id>.json to plugins/<plugin-id>.json in your fork
3. If updating an existing plugin, merge the new version into the versions array
4. Create a PR to the upstream repository

Manual Publishing

If you prefer to publish manually:

swift build -c release

# Sign the dylib (REQUIRED for distributed plugins)
codesign --force --options runtime --timestamp \
  --sign "Developer ID Application: Your Name (TEAMID)" \
  .build/release/libEmacs.dylib

mkdir dist && cp .build/release/libEmacs.dylib dist/
cd dist && zip -r ../osaurus.emacs-1.0.0.zip .
minisign -Slm osaurus.emacs-1.0.0.zip -s minisign.key

Then upload to GitHub Releases and submit a PR to the registry.