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calendar-mcp

calendar-mcp

by atfinke
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Local

calendar-mcp

Local MCP server that exposes Apple Calendar data through an EventKit helper app.

Built entirely by OpenAI GPT-5.4 via Codex.

Install

git clone https://github.com/<your-account>/calendar-mcp.git
cd calendar-mcp
./bootstrap.sh

Related MCP server: mcp-eventkit

Run

npm run start

Permissions

Run calendar_permissions once with prompt: true and access: "full".

The helper app is intended to be built with the project’s normal code signing so macOS can attribute Calendar access to a stable app identity.

If the prompt does not appear from inside Codex, launch the helper app directly once:

open CalendarMCPHelperApp/build/Build/Products/Release/CalendarMCPHelperApp.app

When opened directly, the app will request Calendar access and show a status alert. After that initial grant, the MCP tools can read and write events normally.

Delete safety is intentionally narrow: each calendar_delete_event call can remove only one resolved target. Recurring deletes support one occurrence or one entire series, but not futureEvents or any bulk-delete shape.

calendar_update_event updates an event in place instead of forcing a delete-and-recreate flow. Omitted fields stay unchanged. To clear nullable fields, pass one of clearLocation, clearNotes, clearUrl, or clearTimeZone.

Date Inputs

All tool date inputs accept these wire formats:

  • 2026-04-02 for a local calendar day

  • 2026-04-02T09:30 or 2026-04-02T09:30:00 for a local wall-clock time

  • 2026-04-02T09:30:00-05:00 or 2026-04-02T14:30:00Z for an exact instant

Local date-only and local date-time inputs are interpreted in the helper app's current macOS time zone. Returned event payloads always use ISO-8601 timestamps with timezone offsets.

calendar_list_events treats start and end as the exact time window after parsing those inputs.

occurrenceDate for recurring-event lookups also accepts YYYY-MM-DD. In that case the helper matches the occurrence by local calendar day. When you already have an occurrenceDate timestamp from a previous tool response, prefer passing that exact timestamp back.

MCP config

{
  "mcpServers": {
    "calendar": {
      "command": "node",
      "args": ["/absolute/path/to/calendar-mcp/dist/index.js"],
      "env": {
        "CALENDAR_MCP_HELPER_APP_PATH": "/absolute/path/to/calendar-mcp/CalendarMCPHelperApp/build/Build/Products/Release/CalendarMCPHelperApp.app"
      }
    }
  }
}

Verify

npm run verify

Available Tools

7 tools
calendar_create_eventCreate EventA

Create a calendar event in the default calendar or a specified calendar. start and end accept local dates, local times, or timezone-bearing ISO-8601 timestamps.

Inputs: end (required), start (required), title (required), url, +5 more.

calendar_delete_eventDelete EventA

Delete exactly one calendar target by identifier. For recurring events, choose whether to remove one occurrence or the entire series.

Inputs: scope, occurrenceDate, eventIdentifier, calendarItemIdentifier.

calendar_get_eventGet EventA
Read-only

Fetch a single event by identifier. Pass occurrenceDate when targeting one instance of a recurring series.

Inputs: occurrenceDate, eventIdentifier, externalIdentifier, calendarItemIdentifier.

calendar_list_calendarsList CalendarsA
Read-only

List event calendars available to the helper app.

Inputs: no named parameters.

calendar_list_eventsList EventsA
Read-only

List calendar events in a time window. start and end accept local dates, local times, or timezone-bearing ISO-8601 timestamps.

Inputs: end (required), start (required), calendarIds.

calendar_permissionsCalendar PermissionsB

Check and optionally prompt for Apple Calendar access used by the helper app.

Inputs: access, prompt.

calendar_update_eventUpdate EventA

Update an existing calendar event in place. Omitted fields are left unchanged. Use clear flags to remove location, notes, url, or timeZone.

Inputs: end, url, notes, scope, +14 more.

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

Loading tool schema changelog…

    Deploy Server
    One endpoint for every MCP toolRayrun runs every MCP server behind one URL and holds the credentials. Each call is decided per client, tool, and argument, then recorded.ray.runAd

    TDQS

    A4/5.0

    Scored across 7 tools

    Disambiguation5/5

    Each tool targets a distinct action and resource: permissions for access, list_calendars for available calendars, list_events and get_event for reading events, and create/update/delete for writing events. No two tools perform the same function.

    Naming Consistency4/5

    All tools share the calendar_ prefix and use snake_case, with most following a verb_noun pattern (list_events, create_event). The exception is calendar_permissions, which is noun-only, causing a slight deviation from the otherwise consistent pattern.

    Tool Count5/5

    Seven tools is well within the ideal range for a focused domain. Each tool (permissions, list calendars, list events, get event, create, update, delete) serves a distinct purpose without redundancy or bloat.

    Completeness5/5

    The tool set covers the full lifecycle of calendar event management: permission check, listing calendars, listing/fetching events, and create/update/delete. It also handles recurrence edge cases in get/update/delete, leaving no obvious gaps for typical calendar tasks.

    Maintenance

    ActivityInactive
    ResponsivenessOutdated data

    Resources

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