apple-calendar-mcp

An MCP server that lets an AI assistant read and create events in Apple Calendar — and work out when you actually have time.

macOS only. It talks to EventKit, Apple's own calendar framework, which has no cross-platform equivalent.

claude mcp add apple-calendar -- npx -y @redpop/apple-calendar-mcp

No Xcode, no Swift toolchain, no repository clone. The signed helper binary ships inside the package.

What it does

Most calendar integrations answer what is on my calendar. This one also answers when am I free:

"Find me two hours for deep work this week, outside meetings"
"When could I fit a 30-minute call with someone in Berlin?"
"Book focus time Thursday morning"

find_free_time returns the open gaps, not the busy blocks. It understands that "work" means weekdays during working hours, that "personal" means any day, and that all-day events usually shouldn't count as busy.

It can also keep a buffer around each meeting, because a gap wedged directly between two calls is free on paper and useless in practice.

Alongside that, the usual: list calendars, read events in a range with optional text search, create, update and delete events with location, notes, alarms, all-day or timed. Recurring events come back as individual occurrences, not as the master event — a detail AppleScript-based servers routinely get wrong.

Changing or deleting an occurrence of a recurring event requires saying explicitly whether you mean just that one or every later one too. There is no default for that, because "cancel this Tuesday" and "never again" are not the kind of thing to guess at.

Full parameter reference: docs/tools.md.

Related MCP server: Nextcloud CalDAV MCP Server

Requirements

• macOS 14 (Sonoma) or newer

• Node.js 20 or newer

Nothing else. Building from source additionally needs Xcode Command Line Tools, but installing from npm does not.

Setup

1. Add the server to your client.

claude mcp add apple-calendar -- npx -y @redpop/apple-calendar-mcp

Quit Claude Desktop first (Cmd+Q) — it rewrites its config on exit, so editing while it runs discards your change. Then add to ~/Library/Application Support/Claude/claude_desktop_config.json:

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

Any client that speaks MCP over stdio works. The command is npx, the arguments are -y @redpop/apple-calendar-mcp, and no environment variables are needed.

2. Grant calendar access on first use.

Ask your assistant "what calendars do I have?". A system dialog appears asking to let calendar-helper — not your assistant, the helper itself — access your calendar.

Confirm it, then open System Settings → Privacy & Security → Calendars → calendar-helper → Options… and make sure Full Access is selected, not "Add Only". Read-only access is not enough; the helper checks for full access at startup.

This one dialog is the only manual step, and no package format can take it away. It appears once and survives updates.

Why the dialog says "calendar-helper"

macOS grants calendar permission to the responsible parent process, not to the program actually asking. An AI client that declares no calendar usage in its bundle therefore locks out everything it starts — silently, with no dialog and no entry in System Settings. Several MCP calendar servers work around this by telling you to launch your client from a terminal.

This one doesn't need that. The helper disclaims that inherited responsibility at startup and becomes its own permission identity, so macOS reads the usage description from its bundle and prompts under its own name. One grant then covers every client on the machine.

The full story: docs/architecture.md.

Updating

npx -y @redpop/apple-calendar-mcp@latest

Your calendar grant survives updates: the helper is installed to a fixed path, and macOS binds the grant to that path rather than to the binary's contents.

Uninstalling

Remove the apple-calendar entry from your client's MCP configuration and restart it. Then delete the helper and its permission:

rm -rf ~/Library/Application\ Support/apple-calendar-mcp

The entry under System Settings → Privacy & Security → Calendars stays behind — macOS keeps those even when the binary is gone. Switch it off there if you want it revoked.

Building from source

git clone https://github.com/redpop/apple-calendar-mcp.git
cd apple-calendar-mcp
npm install && npm run build && ./swift/build.sh

Then point your client at dist/index.js with node instead of using npx. Without a Developer ID certificate the helper is signed ad-hoc, and macOS then ties the calendar grant to the exact build — expect a new permission dialog after every rebuild.

Learn more

• docs/architecture.md — how the two halves fit together and the whole TCC permission story

• docs/tools.md — every tool parameter, defaults, and the all-day alarm rule

• docs/cli.md — the standalone calendar-helper command, useful for testing without an MCP client

• docs/troubleshooting.md — common errors and how to fix them

Privacy

Everything runs locally. Calendar data goes from EventKit to the helper to the MCP server to your client, and nowhere else. There is no network code in this project.

License

MIT — see LICENSE.