Control macOS apps via AppleScript/JXA: sanitized commands for Messages, Mail, Finder, and more.
Copy the AI prompt to install this server into Claude Code, Cursor, or another agent β or use 1-click editor setup below.
π‘ Paste the JSON block into your client's configuration file under mcpServers, then restart the application.
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.
JCAppleScript provides three components:
Add JCAppleScript to your Package.swift:
Then add the targets you need:
When embedding untrusted values in script source, escape them first:
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 β Extensions.
Add to your Claude Desktop config (~/Library/Application Support/Claude/claude_desktop_config.json):
Build the server:
| Tool | Description |
|---|---|
execute_applescript | Execute arbitrary AppleScript code β |
execute_jxa | Execute JavaScript for Automation (JXA) code β |
tell_application | Send a command to a specific app via tell block β |
check_script_syntax | Compile a script (AppleScript or JXA) without executing it |
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 |
preview_app_command | Dry-run: show the exact script a command would execute |
get_app_commands | Get detailed command info for a specific app |
β Hidden and disabled when the server runs in safe mode (see below).
| Environment variable | Effect |
|---|---|
JCAS_SAFE_MODE=1 | Disables the arbitrary-code tools (execute_applescript, execute_jxa, tell_application) and registry commands flagged dangerous (e.g. terminal.run_command, safari.run_javascript). Only pre-built, sanitized registry commands remain available. |
JCAS_APP_MANIFESTS=a.json:b.json | 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.
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 |
Implement the ScriptableApp protocol to add support for any scriptable macOS app:
JCAppleScript is designed to grow through community contributions. The app shortcut system uses a standard protocol (ScriptableApp) that makes it easy to:
ScriptableApp for any scriptable macOS appWe're building a browsable registry (similar to npmjs.org) where you can:
Example manifest:
The MCP server loads extra manifests from the JCAS_APP_MANIFESTS environment variable at startup.
Registry command arguments are sanitized before script generation:
\, ", and control characters) so they cannot break out of AppleScript string literals.allowedValues list are dropped.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 β only expose them to clients you trust, or run the server in safe mode.
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