JCAppleScript

A Swift package for executing AppleScript from macOS applications, featuring a built-in MCP server that lets AI assistants control macOS apps through pre-built command shortcuts.

Overview

JCAppleScript provides three components:

1. JCAppleScript (library) - Core AppleScript execution engine
2. AppShortcuts (library) - Registry of pre-built AppleScript commands for popular macOS apps
3. jcas-mcp (executable) - MCP (Model Context Protocol) server for AI-driven app automation

Installation

Swift Package Manager

Add JCAppleScript to your Package.swift:

dependencies: [
    .package(url: "https://github.com/johnnyclem/JCAppleScript.git", branch: "main")
]

Then add the targets you need:

.target(
    name: "YourTarget",
    dependencies: [
        "JCAppleScript",     // Core engine only
        "AppShortcuts",      // App command registry
    ]
)

Quick Start

Using the Core Engine

import JCAppleScript

let engine = AppleScriptEngine.shared

// Execute raw AppleScript
let result = try engine.execute("""
    tell application "Finder"
        display dialog "Hello from Swift!"
    end tell
""")

// Send a command to an application
let output = try engine.tell(application: "Music", command: "play")

// Execute a script file with variable substitution
let fileResult = try engine.executeFile(at: "/path/to/script.scpt", variables: ["Alice", "Hello!"])

Using App Shortcuts

import AppShortcuts

let registry = AppRegistry.shared

// Execute a pre-built command
let result = try registry.executeCommand("messages.send_message", arguments: [
    "recipient": "+15551234567",
    "message": "Hello from JCAppleScript!"
])

// Discover available commands
let commands = registry.commands(forApp: "Reminders")
for cmd in commands {
    print("\(cmd.id): \(cmd.name) - \(cmd.description)")
}

// Search across all apps
let results = registry.searchCommands("send")

Using the MCP Server

The jcas-mcp executable is a Model Context Protocol server that AI assistants (Claude, GPT, etc.) can use to control macOS applications.

Setup with Claude Desktop

Add to your Claude Desktop config (~/Library/Application Support/Claude/claude_desktop_config.json):

{
  "mcpServers": {
    "applescript": {
      "command": "/path/to/jcas-mcp"
    }
  }
}

Build the server:

swift build -c release
# Binary at: .build/release/jcas-mcp

Available MCP Tools

Tool	Description
execute_applescript	Execute arbitrary AppleScript code
tell_application	Send a command to a specific app via tell block
list_running_applications	Get currently running applications
list_registered_apps	Browse all registered app command sheets
search_commands	Search for commands by keyword
run_app_command	Execute a pre-built command by ID
get_app_commands	Get detailed command info for a specific app

Example AI Interaction

User: "Send a message to John saying I'll be late"
AI uses tool: run_app_command
  command_id: "messages.send_message"
  arguments: { "recipient": "John", "message": "I'll be late" }

Supported Applications

JCAppleScript ships with command sheets for 10 built-in macOS apps:

App	Category	Commands	Examples
Messages	Communication	6	Send message, list chats, get participants
Mail	Communication	7	Compose email, search, check mail, list accounts
Reminders	Productivity	7	Create/complete/delete reminders, search, list
Calendar	Productivity	6	Create events, list today's events, upcoming
Notes	Productivity	8	Create/search/append notes, manage folders
Finder	System	12	File operations, folder contents, labels, trash
Safari	Internet	10	Open URLs, manage tabs, run JavaScript, get page content
Music	Media	13	Playback control, playlists, library search, ratings
Terminal	Development	8	Run commands, manage windows/tabs, profiles
System Settings	System	13	Dark mode, volume, notifications, dialogs, system info

Adding Custom App Support

Implement the ScriptableApp protocol to add support for any scriptable macOS app:

import AppShortcuts

struct MyApp: ScriptableApp {
    static let bundleIdentifier = "com.example.myapp"
    static let appName = "MyApp"
    static let description = "My custom application"
    static let category = AppCategory.productivity

    static let commands: [AppCommand] = [
        AppCommand(
            id: "myapp.do_thing",
            name: "Do Thing",
            description: "Performs the thing",
            parameters: [
                CommandParameter(name: "input", description: "The input value"),
            ]
        ) { args in
            let input = args["input", default: ""]
            return """
            tell application "MyApp"
                do thing with "\(input)"
            end tell
            """
        },
    ]
}

// Register at runtime
AppRegistry.shared.register(MyApp.self)

Community App Registry

JCAppleScript is designed to grow through community contributions. The app shortcut system uses a standard protocol (ScriptableApp) that makes it easy to:

• Add new applications - Implement ScriptableApp for any scriptable macOS app
• Extend existing apps - Submit new commands for already-registered apps
• Share command sheets - Export/import app definitions via JSON manifests

We're building a browsable registry (similar to npmjs.org) where you can:

• Browse applications and their supported AppleScript commands
• Submit new commands for existing apps
• Add entirely new applications to the registry
• Generate JSON manifests for integration with other tools

Exporting the Registry

let manifest = AppRegistry.shared.generateManifest()
// Returns a JSON-serializable array of all apps and their commands

Architecture

JCAppleScript/
├── Sources/
│   ├── JCAppleScript/           # Core engine
│   │   ├── AppleScriptEngine.swift
│   │   ├── ScriptResult.swift
│   │   └── ScriptError.swift
│   ├── AppShortcuts/            # App command registry
│   │   ├── AppProtocol.swift    # ScriptableApp protocol
│   │   ├── AppCommand.swift     # Command & parameter types
│   │   ├── AppRegistry.swift    # Central registry
│   │   └── Apps/                # Built-in app sheets
│   │       ├── MessagesApp.swift
│   │       ├── RemindersApp.swift
│   │       ├── FinderApp.swift
│   │       ├── SafariApp.swift
│   │       ├── MailApp.swift
│   │       ├── CalendarApp.swift
│   │       ├── NotesApp.swift
│   │       ├── MusicApp.swift
│   │       ├── TerminalApp.swift
│   │       └── SystemSettingsApp.swift
│   └── JCAppleScriptMCP/       # MCP server
│       ├── main.swift
│       ├── MCPServer.swift
│       ├── MCPTransport.swift
│       └── MCPTypes.swift
├── Tests/
├── Legacy/                      # Original Obj-C implementation
├── Package.swift
└── LICENSE

Requirements

• macOS 13.0+
• Swift 5.9+

Legacy

The original Objective-C implementation (2013) is preserved in the Legacy/ directory for reference. It provided basic NSAppleScript wrapping with variable substitution. The new Swift implementation builds on those concepts while adding the MCP server, app registry, and modern Swift patterns.

License

MIT License - Copyright (c) 2013 John Clem. See LICENSE for details.