jcas-mcp
Click on "Deploy Server".
Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state.
In the chat, type
@followed by the MCP server name and your instructions, e.g., "@jcas-mcpSend a message to John saying I'll be late"
That's it! The server will respond to your query, and you can continue using it as needed.
Here is a step-by-step guide with screenshots.
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:
JCAppleScript (library) - Core AppleScript execution engine
AppShortcuts (library) - Registry of pre-built AppleScript commands for popular macOS apps
jcas-mcp (executable) - MCP (Model Context Protocol) server for AI-driven app automation
Related MCP server: osascript MCP Server
Installation
Swift Package Manager
Add JCAppleScript to your Package.swift:
dependencies: [
.package(url: "https://github.com/johnnyclem/JCAppleScript.git", from: "2.0.0")
]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!"])
// Execute JavaScript for Automation (JXA)
let jxa = try engine.execute("Application('Music').play()", language: .javaScript)
// Check syntax without executing
try engine.checkSyntax("tell application \"Finder\" to activate")
// All execution APIs also have async variants
let asyncResult = try await engine.execute("return 40 + 2")When embedding untrusted values in script source, escape them first:
let userInput = "…"
let script = "display dialog \(AppleScriptString.quoted(userInput))"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.
It is published to the official MCP registry as io.github.johnnyclem/jcas-mcp, and each GitHub release ships a prebuilt jcas-mcp.mcpb bundle (universal macOS binary) that can be installed directly in Claude Desktop via Settings → Extensions.
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-mcpAvailable MCP Tools
Tool | Description |
| Execute arbitrary AppleScript code † |
| Execute JavaScript for Automation (JXA) code † |
| Send a command to a specific app via |
| Compile a script (AppleScript or JXA) without executing it |
| Get currently running applications |
| Browse all registered app command sheets |
| Search for commands by keyword |
| Execute a pre-built command by ID |
| Dry-run: show the exact script a command would execute |
| Get detailed command info for a specific app |
† Hidden and disabled when the server runs in safe mode (see below).
Server Configuration
Environment variable | Effect |
| Disables the arbitrary-code tools ( |
| Colon-separated JSON manifest files with additional community app definitions to load at startup. |
CLI flags: jcas-mcp --manifest prints the full registry as JSON, --version prints the server version, --help shows usage.
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 12 built-in macOS apps:
App | Category | Commands | Examples |
Messages | Communication | 6 | Send message, list chats, get participants |
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 |
Xcode | Development | 20+ | Open/build/run/test projects, schemes, build logs, debugging |
Speech Recognition | System | 3 | Listen for spoken phrases via the system speech engine |
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
ScriptableAppfor any scriptable macOS appExtend 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 and Importing the Registry
// Export all registered apps as manifest JSON
let json = try AppRegistry.shared.exportManifestJSON()
// Import community app definitions from a JSON manifest.
// Manifest commands are declarative script templates with ${param}
// placeholders; argument values are sanitized before substitution.
try AppRegistry.shared.loadManifest(contentsOf: URL(fileURLWithPath: "community.json"))Example manifest:
[
{
"name": "CoolApp",
"bundleIdentifier": "com.example.coolapp",
"description": "A community-contributed app",
"category": "Productivity",
"commands": [
{
"id": "coolapp.greet",
"name": "Greet",
"description": "Show a greeting",
"script": "tell application \"CoolApp\"\n greet \"${who}\"\nend tell",
"parameters": [
{"name": "who", "description": "Who to greet", "required": true, "type": "string"}
]
}
]
}
]The MCP server loads extra manifests from the JCAS_APP_MANIFESTS environment variable at startup.
Security Model
Registry command arguments are sanitized before script generation:
String, file-path, and date arguments are escaped (
\,", and control characters) so they cannot break out of AppleScript string literals.Integer and boolean arguments are strictly validated/normalized — malformed values are rejected at validation and fall back to declared defaults during generation.
Values outside a parameter's
allowedValueslist are dropped.Arguments that don't correspond to a declared parameter are discarded.
Commands that execute caller-supplied code (Terminal shell commands, Safari JavaScript) are flagged dangerous and can be disabled wholesale with JCAS_SAFE_MODE=1. Use the preview_app_command tool to inspect the exact script a command will run before executing it.
Note that execute_applescript, execute_jxa, and tell_application execute arbitrary code by design — only expose them to clients you trust, or run the server in safe mode.
Architecture
JCAppleScript/
├── Sources/
│ ├── JCAppleScript/ # Core engine
│ │ ├── AppleScriptEngine.swift
│ │ ├── AppleScriptSanitizer.swift
│ │ ├── ScriptResult.swift
│ │ └── ScriptError.swift
│ ├── AppShortcuts/ # App command registry
│ │ ├── AppProtocol.swift # ScriptableApp protocol
│ │ ├── AppCommand.swift # Command & parameter types + sanitization
│ │ ├── AppDefinition.swift # Instance-based app description
│ │ ├── AppManifest.swift # JSON import/export
│ │ ├── 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
└── LICENSERequirements
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.
This server cannot be deployed
Maintenance
Related MCP Connectors
Use your own Mac from ChatGPT, Claude or Codex: files, commands, documents, and a browser.
MCP connector that lets ChatGPT list, search, and run your Apple Shortcuts via a local Mac agent
Automate 1,000+ services from any MCP-compatible AI agent: build Applets, run actions and queries.
Operate Linux, macOS and Windows from your LLM. Every action runs through an auditable allowlist.
Related MCP Servers
- AlicenseBqualityDmaintenanceEnables AI agents to interact with macOS applications (Finder, Mail, Contacts, Reminders, Notes, Calendar, TextEdit) using AppleScript. Allows AI assistants to perform tasks like searching contacts, managing files, checking email, and creating reminders through natural language.241MIT
- FlicenseAqualityDmaintenanceEnables the execution of AppleScript and JavaScript for Automation (JXA) on macOS to control applications, system events, and shell commands. It provides native automation capabilities with a security layer that permits most operations while specifically blocking file deletion commands.16-
- AlicenseAqualityCmaintenanceEnables Large Language Models to automate macOS applications and execute AppleScript commands through natural language. It features built-in security protections including application allowlists and dangerous pattern detection to prevent unauthorized or risky system operations.2MIT
- AlicenseNot gradedqualityFmaintenanceEnables AI assistants to automate macOS desktop tasks including mouse control, keyboard input, screenshots, window management, and UI interaction.6 npm415MIT