caldav-mcp

An MCP server that gives Claude (Desktop/Cowork/Code) access to plain CalDAV calendars — the on-prem/self-hosted calendars (SOGo, Nextcloud, Radicale, Baïkal, Synology, …) not covered by the official Google/M365 connectors. Sibling project to imap-mcp and built on the same safety model.

Safety model

All guardrails live in accounts.json — not in prompts or tool descriptions — so they hold even if calendar content tries prompt injection:

1. Read tools always work: list calendars, search events, read an event.

2. Write tools (create/update/cancel events) require "allow_writes": true on the account; without it they refuse before any network connection.

3. No delete. cancel_event only sets STATUS:CANCELLED (reversible with cancelled=false); nothing is ever removed from the server.

4. No invitations. Events can never carry attendees, so the CalDAV server can never send scheduling emails (iTIP/iMIP) on Claude's behalf.

Related MCP server: calendar-mcp

Setup

bash setup.sh        # macOS/Linux — creates .venv, installs deps, registers in Claude Desktop
.\setup.ps1          # Windows

Then edit accounts.json (gitignored) with your CalDAV URL and username, store the password in the OS keychain, and verify:

.venv/bin/python server.py --set-password '<account>'
.venv/bin/python server.py --check

Restart Claude Desktop. For Claude Code, register with:

claude mcp add caldav -- "$PWD/.venv/bin/python" "$PWD/server.py"

Account config

{
  "accounts": {
    "crewcast": {
      "url": "https://mail.crewcast.dk/SOGo/dav/",
      "username": "you@crewcast.dk",
      "allow_writes": false
    }
  }
}

Tools

Tests

.venv/bin/python test_server.py

Offline — no calendar server or credentials needed; prints per-check status and ALL CHECKS PASSED.