@mgcrea/mcp-apple-calendar

Model Context Protocol server for the macOS Apple Calendar app.

Unofficial. Not affiliated with Apple. It reads the Calendar store already on your Mac.

One lane for reads, one for writes

• Index lane — read-only SQLite over Calendar.sqlitedb. Every read goes through it.
• Apple Events lane — writes only. There is no jxa/read.ts in this package, and a test asserts there never will be.

This is the inverse of Notes. Notes shipped on Apple Events because search took 97 ms. Calendar cannot: a ±90-day range query over 1,349 events takes 3,355 ms over Apple Events, whose is worse and unstable, and every per-property bulk fetch costs ~1.8 s whichever property it is — so the cost cannot be amortised the way Notes amortises a bulk fetch. The store opens read-only in 1 ms. Calendar needs the file lane for speed, not capability.

It does not need EventKit, which is why the companion app stays a pure broker rather than linking a framework that would drag its own TCC prompt in.

| Permission | Needed for | Without it | | ------------------------- | ----------- | ----------------------------------------- | | Full Disk Access | all reads | nothing works — there is no read fallback | | Automation → Calendar | writes only | reads are unaffected |

Neither is granted to Calendar.app — it is the reader that needs permission. Grant Full Disk Access to whatever launches the server (Terminal, iTerm, VS Code, Claude), then restart it.

With writes off — the default — no Automation prompt appears at all. A read-only Calendar server needs exactly one permission.

Tools

Read: diagnostics, list_accounts, list_calendars, list_events, search_events, get_event.

Write, registered only when APPLE_CALENDAR_ALLOW_WRITES=1 — with the flag off they are invisible to the model, not merely refused: create_event, update_event, delete_events.

Configuration

| Variable | Default | | | ----------------------------------------------- | ---------- | --------------------------------------------- | | APPLE_CALENDAR_ALLOW_WRITES | off | Register the mutating tools. | | APPLE_CALENDAR_ACCOUNTS | all | Read-side allowlist, comma-separated. | | APPLE_CALENDAR_CALENDARS | all | Read-side allowlist, comma-separated. | | APPLE_CALENDAR_DEFAULT_CALENDAR | Calendar's | Calendar a new event goes to when none named. | | APPLE_CALENDAR_DEFAULT_RANGE_DAYS | 7 | An unbounded default would scan a decade. | | APPLE_CALENDAR_MAX_RANGE_DAYS | 366 | Ceiling on a caller-supplied range. | | APPLE_CALENDAR_DEFAULT_EVENT_DURATION_MINUTES | 60 | Used when a write names no end. | | APPLE_CALENDAR_INCLUDE_DECLINED | off | Include declined events in reads. | | APPLE_CALENDAR_INCLUDE_CANCELLED | off | Include cancelled events in reads. | | APPLE_CALENDAR_TIMEZONE | system | Override the zone ranges are resolved in. | | APPLE_CALENDAR_INDEX_MODE | auto | auto | ro | immutable | off. | | APPLE_CALENDAR_STORE | auto | Explicit Calendar.sqlitedb path. | | APPLE_CALENDAR_OSASCRIPT_TIMEOUT_MS | 30000 | Sized for the first-run permission prompt. |

Notes that will bite you

• ~/Library/Calendars does not exist. The store is ~/Library/Group Containers/group.com.apple.calendar/Calendar.sqlitedb.
• Recurrence lives in a cache table. A naive SELECT ... FROM CalendarItem over a date range misses expanded repeats; the range query unions items carrying no recurrence rule with everything in the cache. 456 of 489 cached parents carry no rule of their own.
• Dates are seconds since 2001, not 1970 — CalendarItem.last_modified and orig_date both.
• A floating time zone is not the system one. Anything matching GMT±HHMM is a real zone; treating the rest as floating is what stops a two-hour silent shift.
• Writes always go through Apple Events, never the store, which the app holds open and syncs.

Licence

MIT.