Nextcloud Calendar

Creates, updates, and deletes calendar events through CalDAV protocol integration with Nextcloud servers. Implements RFC 4791 CalDAV specification to directly manipulate iCalendar (ICS) objects on the Nextcloud backend, enabling atomic event operations with full property support (title, description, start/end times, recurrence rules, attendees). Uses HTTP-based WebDAV operations (PUT/DELETE) to persist changes directly to the calendar collection on the server.

Lists all calendars available to the authenticated user by querying the CalDAV PROPFIND method on the principal collection. Retrieves calendar metadata including display names, colors, descriptions, and access control properties (read-only vs read-write). Parses XML responses from the CalDAV server to construct a structured inventory of available calendar collections.

Retrieves events from a calendar using CalDAV REPORT method with CALDAV:calendar-query filters. Supports filtering by date range (DTSTART/DTEND), event properties (summary, description), and recurrence expansion. Parses iCalendar (ICS) responses to construct structured event objects with full property access. Handles recurring events by expanding instances within the requested time window.

Manages event attendees by manipulating ATTENDEE properties in iCalendar objects. Adds, removes, or modifies attendee entries with role (REQ-PARTICIPANT, OPT-PARTICIPANT), participation status (NEEDS-ACTION, ACCEPTED, DECLINED), and RSVP flags. Updates the event's ORGANIZER property and sends invitations through the Nextcloud Calendar app's notification system. Handles attendee responses by updating PARTSTAT (participation status) in the event record.

Modifies individual event properties (title, description, location, start/end times, categories, alarms) by parsing and updating iCalendar (RFC 5545) objects. Preserves existing properties while updating specified fields, maintaining iCalendar validity and server-side constraints. Handles timezone-aware datetime conversions and validates property formats before submission. Uses CalDAV PUT to atomically replace the entire event object with updated properties.

Registers calendar operations as MCP (Model Context Protocol) tools with JSON Schema definitions, enabling LLM agents to invoke calendar functions through a standardized interface. Each tool (create event, list calendars, query events, etc.) is defined with input schema, output schema, and natural language descriptions. The MCP server translates tool invocations from the LLM into CalDAV operations, handling parameter validation and error mapping back to the agent.

Manages authentication to Nextcloud CalDAV servers using HTTP Basic Auth or Nextcloud app tokens. Stores and retrieves credentials securely (or as plaintext if not configured), constructs Authorization headers for CalDAV requests, and handles authentication failures with appropriate error messages. Supports both username/password and token-based authentication schemes compatible with Nextcloud's authentication system.

Converts between local, UTC, and iCalendar TZID-based datetime representations. Parses DTSTART/DTEND properties with timezone identifiers (e.g., TZID=America/New_York), converts to UTC for storage, and reconstructs timezone-aware datetimes for display. Handles daylight saving time transitions and validates timezone identifiers against the system or Nextcloud server's timezone database.

Parses iCalendar RRULE (recurrence rule) syntax to understand recurring event patterns (daily, weekly, monthly, yearly with complex rules like 'every 2nd Tuesday'). Expands recurring events into individual instances within a specified date range, handling exceptions (EXDATE) and modifications (RECURRENCE-ID). Validates RRULE syntax and handles edge cases like leap years and month boundaries.