CalDAV MCP Server

CalDAV MCP Server

CalDAV MCP Server is a Model Context Protocol server for managing iCloud Calendar events, including native support for multiple VALARM reminders on one event.

iCloud Calendar is the only provider officially supported and manually validated in the first release. The server works with any MCP client that supports stdio or Streamable HTTP.

This independent project is not affiliated with, authorized, sponsored, or approved by Apple Inc. Apple and iCloud are trademarks of their respective owner.

Quick start

Create an Apple app-specific password, then pick the option for your client.

Claude Desktop (one click, no Node.js install): download caldav-mcp.mcpb, open it with Claude Desktop, and enter your Apple Account email and app-specific password. See Claude Desktop extension.

Any other `stdio` client: install Node.js 22 or newer and add this server to a JSON-configured MCP client such as Gemini CLI or Claude Code:

{

"mcpServers": { "icloud-calendar": { "command": "npx", "args": ["--yes", "@lukegskw/caldav-mcp@latest"], "env": { "CALDAV_USERNAME": "user@example.com", "CALDAV_PASSWORD": "xxxx-xxxx-xxxx-xxxx" } } } }

Restart the client and confirm that it lists six calendar tools. See client-specific setup and Docker deployment below. Keep the configuration file private because it contains the app-specific password.

Navigation

• About
• Features
• MCP tools
• Tech stack
• Installation
• Configuration
• MCP client setup
• Verification
• Limitations
• Contributing
• Releasing

About

The server connects one configured account to iCloud through CalDAV. It discovers the account's calendars and exposes normalized read and write operations through MCP.

Updates preserve the complete iCalendar resource, including unknown properties, Apple extensions, VTIMEZONE, recurrence exceptions, and alarms omitted from a patch. Writes use opaque resource identifiers and ETags instead of assuming that a CalDAV filename matches an event UID.

Calendar resources are processed in memory. The server has no telemetry and no application database, and raw iCalendar is returned only when explicitly requested.

Features

• Discovers calendars available to the configured iCloud account.
• Lists events in semi-open time ranges and expands recurring occurrences.
• Creates timed, all-day, and recurring events.
• Supports zero, one, or multiple display alarms per event.
• Reads and writes Apple Calendar travel time (X-APPLE-TRAVEL-DURATION).
• Emits the Apple alarm extensions expected by iCloud Calendar.
• Reads events by opaque resource ID or by calendar ID and UID.
• Applies partial updates while preserving omitted and unknown iCalendar data.
• Uses ETags for optimistic concurrency on updates and deletions.
• Rejects isolated recurrence mutations instead of changing the complete series.
• Redacts credentials, raw calendar content, and CalDAV paths from logs and errors.
• Runs as a non-root container with a read-only root filesystem configuration.
• Supports stdio and Streamable HTTP MCP transports.

MCP tools

list_calendars

Lists the calendars discovered for the configured account. Each result includes an opaque calendar_id, display name, description, timezone, and best-effort write status.

list_events

Lists events in a semi-open interval and expands recurring occurrences. The maximum range is 366 days, the default page size is 100, and the maximum page size is 500. Results use a deterministic chronological order. Pagination cursors are opaque and do not represent a snapshot when events are modified during traversal.

Example input:

{

"calendar_id": "opaque-calendar-id", "start": "2026-09-01T00:00:00Z", "end": "2026-10-01T00:00:00Z", "timezone": "Europe/Berlin", "limit": 100 }

get_event

Reads an event by resource_id, or by a calendar_id and UID pair. Raw iCalendar is excluded by default and can be requested with include_raw_ical: true for controlled diagnostics.

create_event

Creates an event and reads back the representation stored by the server.

Timed event with two alarms:

{

"calendar_id": "opaque-calendar-id", "summary": "Buy Shinkansen tickets", "start": { "date_time": "2026-09-06T03:00:00+02:00", "timezone": "Europe/Berlin" }, "end": { "date_time": "2026-09-06T03:30:00+02:00", "timezone": "Europe/Berlin" }, "description": "Smart-EX", "location": null, "alarms": [ { "minutes_before": 1440, "action": "DISPLAY" }, { "minutes_before": 0, "action": "DISPLAY" } ], "rrule": null }

All-day event with an exclusive end date:

{

"calendar_id": "opaque-calendar-id", "summary": "Trip", "start": { "date": "2026-09-06" }, "end": { "date": "2026-09-08" }, "alarms": [] }

Recurring events accept an RFC 5545 rule without the RRULE: prefix:

{

"calendar_id": "opaque-calendar-id", "summary": "Weekly planning", "start": { "date_time": "2026-09-07T09:00:00+02:00", "timezone": "Europe/Berlin" }, "end": { "date_time": "2026-09-07T09:30:00+02:00", "timezone": "Europe/Berlin" }, "rrule": "FREQ=WEEKLY;BYDAY=MO;COUNT=10" }

Timed event with 30 minutes of Apple Calendar travel time:

{

"calendar_id": "opaque-calendar-id", "summary": "Dentist", "start": { "date_time": "2026-10-05T10:00:00+02:00", "timezone": "Europe/Amsterdam" }, "end": { "date_time": "2026-10-05T10:30:00+02:00", "timezone": "Europe/Amsterdam" }, "travel_minutes": 30 }

travel_minutes sets a fixed travel duration before the event. In this example, travel starts at 09:30 and the appointment stays at 10:00–10:30. The server accepts whole minutes from 1 to 1,440 for timed events; omit the field or use null when creating an event without travel time. It does not calculate routes or change the event's start, end, or alarms.

The duration is stored in Apple's X-APPLE-TRAVEL-DURATION extension. Display in other calendar clients depends on their support for that extension. Returned events include travel_minutes, rounded to the nearest whole minute, or null when the duration is missing, invalid, or rounds to zero.

update_event

Patches an event or the master event of a recurring series. Omitted fields are preserved, null removes a nullable field, and alarms: [] removes all alarms. An optional expected_etag prevents overwriting a newer server version.

For travel time, omit patch.travel_minutes to keep the current value, set it to a number to replace the duration, or set it to null to remove the duration and related Apple routing metadata. For example, "patch": { "travel_minutes": null } clears travel time. When converting an event with travel time to all-day, include travel_minutes: null alongside the new start and end dates. Existing recurrence exceptions retain their own travel settings.

delete_event

Deletes an event or complete recurring series, optionally requiring an observed ETag. Deleting a single expanded occurrence is not supported in the current release.

Tech stack

• Node.js 22+ (see Node.js requirements)
• TypeScript with strict project rules
• Model Context Protocol TypeScript SDK
• tsdav
• ical.js
• Zod
• Vitest
• pnpm
• Docker

Installation

Prerequisites

• An iCloud account with Calendar enabled.
• Two-factor authentication enabled for the Apple Account.
• An app-specific password.
• Docker and Docker Compose for container deployment, Node.js 22+ for npx, or Claude Desktop for the one-click extension.
• pnpm is required only when building from source. Corepack and CI use the version pinned in package.json.

Node.js requirements

engines.node in package.json is >=22. Node.js 20 reached end of life in April 2026 and is not supported; npm prints an EBADENGINE warning on older versions. Check the version your MCP client will use with node --version. Desktop clients may use a different node than your terminal, so if a client cannot start the server, point it at the absolute path of a Node.js 22+ npx (command -v npx on macOS/Linux, where npx on Windows).

npm / npx

No global install or repository clone is required. MCP clients can launch the latest published package directly:

CALDAV_USERNAME='user@example.com' \

CALDAV_PASSWORD='xxxx-xxxx-xxxx-xxxx' \ npx --yes @lukegskw/caldav-mcp@latest

The command waits for MCP messages on stdin and normally prints nothing to stdout. In practice, add it to the client configuration as shown in MCP client setup. For reproducible environments, replace latest with an exact published version such as X.Y.Z.

Docker Compose

The recommended installation uses the published multi-architecture image:

ghcr.io/lukegskw/caldav-mcp:latest

Download the Compose example:

curl -O https://raw.githubusercontent.com/lukegskw/caldav-mcp/main/compose.example.yaml

Provide the Apple Account email and app-specific password, then start the service:

export CALDAV_USERNAME='user@example.com'

export CALDAV_PASSWORD='xxxx-xxxx-xxxx-xxxx' docker compose -f compose.example.yaml up -d

To publish a different host port, set:

export CALDAV_MCP_PUBLISHED_PORT=18100

docker compose -f compose.example.yaml up -d

The latest tag follows the newest stable release. Stable releases also publish an exact tag such as 0.1.6 and a minor-series tag such as 0.1. The Compose example pins latest by digest so deployments are