Apple Calendar

LIST! CREATE! UPDATE! DELETE!

Apple Calendar MCP is a Model Context Protocol server that hands Claude (and any other MCP client) the keys to the macOS Calendar.app that's already on your Mac. It speaks AppleScript under the hood — no cloud API, no CalDAV account setup, no telemetry — and exposes six focused tools for listing, searching, creating, updating, and deleting events.

If you want Claude to actually do things on your calendar instead of pasting iCal blobs at you, this is it.

GitHub · Issues · Changelog · Security · Contributing · Vision

Install

Runtime: Node 22.14+, macOS (Calendar.app required).

claude mcp add apple-calendar -- npx -y apple-calendar-mcp

Or use the npx one-liner directly — no install step — and let your MCP client spawn it on demand (see Quick start below).

Quick start

Add this to your Claude Code MCP config (~/.claude.json or a project-local .mcp.json):

{
  "mcpServers": {
    "apple-calendar": {
      "command": "npx",
      "args": ["-y", "apple-calendar-mcp"]
    }
  }
}

Then ask Claude things like:

• "What's on my calendar this week? Summarize anything that overlaps."
• "Create a 30-minute focus block tomorrow at 9am titled 'Deep work — refactor.'"
• "Find every event mentioning '1:1' in the last month and list the attendees."
• "Move my Friday 3pm dentist appointment to next Tuesday at 10am."

Default: the server runs over stdio only. Your calendar never leaves your Mac.

macOS permissions

The first time a tool runs, macOS will prompt you to grant Calendar access to the controlling process (the terminal or IDE that spawned npx). Approve it.

If you see "not authorized" or error -1743 / -1744 later:

1. Open System Settings → Privacy & Security → Automation.
2. Find your terminal / IDE (Terminal.app, iTerm, VS Code, Cursor, Claude Code…).
3. Enable the Calendar toggle underneath it.

You may also need Privacy & Security → Calendars enabled for the same app. If you launched via npx, the controlling process is whichever app spawned it — not npx itself.

Tools

Tool	Description	Key args
list_calendars	All calendars with name + writable	—
list_events	Events in a date range	start_date, end_date, calendar_name?, limit?
search_events	Substring match across title, location, notes	query, start_date?, end_date?, limit?
create_event	Create a new event on any writable calendar	title, start_date, end_date, calendar_name?, location?, notes?, url?, all_day?
update_event	Update any subset of fields	event_id, plus any optional field from create_event
delete_event	Delete by id	event_id

All dates are ISO 8601 (2026-04-21T14:30:00Z or 2026-04-21T10:30:00-07:00). Event id values are Calendar.app uid strings — stable across calls, safe to stash and reuse.

Security defaults

Apple Calendar MCP treats every string arriving from an MCP tool call as untrusted. That matters because AppleScript has no prepared-statement equivalent.

• AppleScript string escaping. Every user-supplied string (event titles, notes, calendar names, event ids, etc.) passes through escapeAppleScriptString, which escapes \ and " before wrapping in quotes. This is the only user-input path into osascript, and the function is unit-tested against injection payloads like "; do shell script "rm -rf /"; --.
• stdio is the transport. Everything human-readable goes to stderr. Stdout is reserved for the MCP protocol. Don't console.log in tool code — that corrupts the transport.
• Stable event ids. id is the Calendar.app uid, not a list-index or hash. It survives restarts, moves between calendars, and edits.
• What this server does NOT do: no network listener, no HTTP endpoint, no CalDAV/iCloud/Google sync, no telemetry, no background processes. Your MCP client spawns osascript, gets a reply, and that's the end of it.

See SECURITY.md for the full threat model.

Highlights

• Zero-config from Claude Code — one claude mcp add line and you're done.
• Local-only — no cloud, no CalDAV client, no background daemon.
• Six tools, nothing hidden — list calendars, list events, search, create, update, delete.
• AppleScript-injection hardened — every string is escaped, every escape is unit tested.
• Stable event ids across calls and sessions.
• ISO 8601 everywhere — timezone-aware inputs, deterministic outputs.
• Unicode-clean — emoji, CJK, and newlines round-trip through osascript without mangling.

Development

git clone https://github.com/yongzhe-wang/apple-calendar-mcp.git
cd apple-calendar-mcp
pnpm install
pnpm test
pnpm build
pnpm check

• pnpm dev — rebuild on change
• pnpm test — run the unit suite (pure helpers only, no Calendar.app required)
• pnpm lint / pnpm lint:fix — oxlint
• pnpm format / pnpm format:check — oxfmt
• pnpm typecheck — tsc --noEmit
• pnpm knip — unused code/deps
• pnpm check — typecheck + lint + format:check + knip (same gate as CI)

Project layout:

src/
  index.ts           # MCP server bootstrap (stdio transport)
  applescript.ts     # osascript bridge + string/date escaping helpers
  errors.ts          # user-facing error formatting
  types.ts           # zod schemas for tool inputs
  tools/             # one file per MCP tool
test/                # unit tests for pure helpers (no Calendar.app required)

How it works

Apple Calendar MCP runs osascript -e <script> for each tool call. It builds the AppleScript source in TypeScript, escapes every untrusted field through escapeAppleScriptString, and reads back a single string result.

To survive arbitrary user text inside that result (commas, newlines, quotes, emoji), the scripts emit fields joined by ASCII control bytes — record separator 0x1E between rows and unit separator 0x1F between fields. These bytes virtually never appear in real calendar data, so parsing becomes a dumb split — no CSV/JSON quoting gymnastics, no ambiguity.

Why not a Swift/EventKit helper binary? EventKit is cleaner, but shipping a signed native binary through npm is a packaging nightmare, and AppleScript + osascript is already on every Mac. The trade-off is verbose scripts; the win is zero-dependency distribution.

Why another Apple Calendar MCP?

There are a handful of existing MCP servers that try to reach macOS Calendar.app. Most of them fall over in at least one of the same ways. This table is the landscape as of April 2026:

Repo	Approach	Status	Where it breaks
supermemoryai/apple-mcp	AppleScript (TS)	archived Aug 2025	locale-dependent date "${start.toLocaleString()}"; incomplete string escape (quotes before backslashes); read path returns a hardcoded dummy event
Omar-V2/mcp-ical	EventKit (Python)	active, 24 open issues	timezone bugs on list/create/delete (issues #17, #20, #25, #18); requires launching Claude from terminal for the permission prompt
joshrutkowski/applescript-mcp	AppleScript (TS)	stale since Apr 2025	zero escaping on event title — direct interpolation into AppleScript source
steipete/macos-automator-mcp	Generic AppleScript runner (TS)	active	not calendar-specific; escaping responsibility pushed entirely to the LLM caller
PsychQuant/che-ical-mcp	Native Swift EventKit	active	feature-rich but requires downloading a signed binary and a PlistBuddy + codesign ritual per IDE

Systemic problems across the category

1. AppleScript injection. Most AppleScript-based servers either don't escape user input at all, or escape in the wrong order (quotes before backslashes, which is broken). A malicious event title can exit the AppleScript string and run arbitrary shell.
2. Locale-sensitive date literals. AppleScript's date "Monday, April 21, 2026 at 10:00:00 AM" parses differently in non-US locales. Several servers ship this bug.
3. Timezone handling in EventKit servers. Moving off AppleScript doesn't fix timezone correctness — the Python EventKit option has open bugs on all-day events, recurring deletions, and ISO 8601 parsing.
4. Permission UX is uniformly painful. Servers variously require codesign invocations, running Claude from a terminal, or a special launch path to trigger the TCC prompt.
5. stdout-vs-stderr discipline is undocumented. MCP speaks JSON-RPC on stdout; a stray console.log in server code silently corrupts the transport. No competitor README flags this.
6. No published threat model. None of the above ship a SECURITY.md that names AppleScript injection, permission scope, or the stdout invariant.

What this server does differently

• **escapeAppleScriptString escapes \ before ", tested with adversarial payloads** including "; do shell script "rm -rf /"; -- in every string field.
• isoToAppleScriptDate is built from epoch seconds against a fixed 1970 anchor so it parses identically on every macOS locale.
• Event id is Calendar.app's own uid property — stable across app restarts and (with the copy-then-delete update path) survives calendar moves cleanly.
• console.log is banned in server code paths. All diagnostics go to stderr. stdout is reserved for the MCP transport.
• Every tool argument is validated by zod at the boundary.
• osascript runs with a 16 MiB output cap to bound memory on runaway scripts.
• SECURITY.md documents the threat model — AppleScript injection, permission scope, stdout transport.

Honest gaps

We're not feature-complete. Today this server does not cover:

• Reminders.app (separate AppleScript target — tracked for v0.2).
• Recurring-event expansion UI — RRULE strings are returned raw; client-side filtering only. Cross-calendar moves of recurring events are explicitly blocked with a clear error (tracked for v0.2) rather than silently flattening the series.
• Attendee management, conflict detection, batch operations — che-ical-mcp has these if you need them.
• Sequoia TCC parent-process permission attribution is not documented in the install section yet.

If you need any of the above today, che-ical-mcp or mcp-ical are your better options. If you want a small, correctness-first calendar bridge that won't eat your events, this is it.

FAQ

Does this need iCloud? No. It talks to whatever calendars are configured in Calendar.app — iCloud, Google (via Calendar.app), local "On My Mac", CalDAV, whatever. If Calendar.app can see it, this server can.

Does it need Full Disk Access? No. Only Automation access to Calendar (and, on some macOS versions, Privacy & Security → Calendars).

Linux / Windows support? No. This server is Mac-only by design — it uses osascript and Calendar.app. The package.json declares "os": ["darwin"] so npm install on other platforms is a fast fail.

How are event ids stable? The id is the Calendar.app uid, a UUID-ish string that persists across edits, calendar moves, and Calendar.app restarts. It's the same value Calendar.app uses in CalDAV sync.

Recurring events? The current tools read each occurrence as Calendar.app presents it. You can update or delete a specific occurrence by its uid, but this server does not (yet) expose recurrence-rule editing. See VISION.md for the roadmap.

Does anything get sent over the network? No. Zero network listeners, zero outbound calls. The server reads stdin, writes stdout, and shells out to osascript — that's it.

Contributing

Bug reports and PRs welcome. See CONTRIBUTING.md for setup, review, and scope guidelines.

License

MIT © Yongzhe Wang 2026