Tool reference

All 22 tools: 10 read, 12 write. With CALDAV_READ_ONLY=true the write tools are not registered at all — they do not appear in tools/list.

All 22 are registered unless you say otherwise. CALDAV_ALLOW_TOOLS and CALDAV_DENY_TOOLS narrow the list to the ones you want, and CALDAV_ALLOW_TOOLS=essential selects the 7 marked essential below — see choosing the tools that load.

👤 marks a tool that asks a person before it acts, through MCP elicitation — a dialog the model cannot answer on its behalf. Where the client cannot show one, it falls back to a two-call confirm_token bound to the exact target and expiring after five minutes, and says which of the two it was. ELICITATION=false takes that fallback deliberately; it never removes the guard. See Asking a person.

Every tool declares all four MCP annotations — readOnlyHint, destructiveHint, idempotentHint, openWorldHint. They are a hint a client may ignore; the dialog is enforced here and cannot be, which is why the two lists are not the same one.

Read tools

list_calendars

List the calendars — read-only, essential

Every calendar this server may use, with the id to pass to the other tools. Always asks the server rather than answering from a cache — being current is this tool’s whole job.

Takes no parameters.

get_server_info

What the connected CalDAV server can do — read-only

Reports the DAV compliance tokens, which components each calendar accepts, and whether the optional features this server relies on actually work here. The first thing to run when something behaves differently than expected — CalDAV implementations differ more than the specification suggests.

Takes no parameters.

list_events

List events in a time range — read-only, essential

Events between two points in time, from every calendar this server may see or from the ones named. Recurring events are expanded into their individual occurrences, so each one has its own id and can be changed on its own. Defaults to the next 30 days.

Parameter	Type	Required	Description
from	string	no	Start of the window. Defaults to now.
to	string	no	End of the window. Defaults to 30 days after from.
timezone	string	no	IANA zone for timestamps that carry no offset, e.g. "Europe/Berlin". Defaults to CALDAV_TIMEZONE. Refused together with a value that already carries an offset.
calendars	string[]	no	Which calendars to look in. Leave it out for all of them. A calendar outside CALDAV_CALENDARS is refused rather than silently skipped.
limit	integer	no	Entries to return, at most 500. Defaults to CALDAV_MAX_EVENTS.
after	string	no	The truncated.next_cursor of a previous call, to continue where it stopped. The window has to be the same one.

get_event

Read one event in full — read-only, essential

The complete event behind an id from a listing: the untruncated description, every reminder, every attendee, every attachment as metadata. An occurrence id answers with that one instance; a series id answers with the series and its rule.

Parameter	Type	Required	Description
id	string	yes	An id from a listing tool. Not meant to be built by hand.

search_events

Search events by text — read-only, essential

Finds events whose summary, description or location contains a term. The search runs on the CalDAV server, one request per field and per calendar — the specification combines several field filters with AND, so asking for all three at once would only match entries carrying the term in every one of them.

Parameter	Type	Required	Description
query	string	yes	The term to look for. Matching is the server’s to define.
fields	"SUMMARY" | "DESCRIPTION" | "LOCATION"[]	no	Which fields to search. Defaults to all three.
from	string	no	ISO 8601: "2026-09-07" for a whole day, "2026-09-07T09:00:00" in the timezone argument or CALDAV_TIMEZONE, or "2026-09-07T09:00:00+02:00".
to	string	no	ISO 8601: "2026-09-07" for a whole day, "2026-09-07T09:00:00" in the timezone argument or CALDAV_TIMEZONE, or "2026-09-07T09:00:00+02:00".
timezone	string	no	IANA zone for timestamps that carry no offset, e.g. "Europe/Berlin". Defaults to CALDAV_TIMEZONE. Refused together with a value that already carries an offset.
calendars	string[]	no	Which calendars to look in. Leave it out for all of them. A calendar outside CALDAV_CALENDARS is refused rather than silently skipped.
limit	integer	no	Entries to return, at most 500. Defaults to CALDAV_MAX_EVENTS.

get_free_busy

When the calendar is busy — read-only, essential

Busy periods in a time range — start and end only, no titles and no attendees. The datasparing way to ask "when am I free": nothing anybody else wrote comes back, so there is no untrusted content in the answer at all.

Parameter	Type	Required	Description
from	string	no	ISO 8601: "2026-09-07" for a whole day, "2026-09-07T09:00:00" in the timezone argument or CALDAV_TIMEZONE, or "2026-09-07T09:00:00+02:00".
to	string	no	ISO 8601: "2026-09-07" for a whole day, "2026-09-07T09:00:00" in the timezone argument or CALDAV_TIMEZONE, or "2026-09-07T09:00:00+02:00".
timezone	string	no	IANA zone for timestamps that carry no offset, e.g. "Europe/Berlin". Defaults to CALDAV_TIMEZONE. Refused together with a value that already carries an offset.
calendars	string[]	no	Which calendars to look in. Leave it out for all of them. A calendar outside CALDAV_CALENDARS is refused rather than silently skipped.

list_tasks

List tasks — read-only

Tasks with a start or due date inside a time range. Tasks with no date at all are not returned by a time-range query — the CalDAV specification defines the filter against the dates, and a task with none of them matches no window.

Parameter	Type	Required	Description
from	string	no	ISO 8601: "2026-09-07" for a whole day, "2026-09-07T09:00:00" in the timezone argument or CALDAV_TIMEZONE, or "2026-09-07T09:00:00+02:00".
to	string	no	ISO 8601: "2026-09-07" for a whole day, "2026-09-07T09:00:00" in the timezone argument or CALDAV_TIMEZONE, or "2026-09-07T09:00:00+02:00".
timezone	string	no	IANA zone for timestamps that carry no offset, e.g. "Europe/Berlin". Defaults to CALDAV_TIMEZONE. Refused together with a value that already carries an offset.
calendars	string[]	no	Which calendars to look in. Leave it out for all of them. A calendar outside CALDAV_CALENDARS is refused rather than silently skipped.
include_completed	boolean	no	Defaults to false, which leaves completed tasks out.
limit	integer	no	Entries to return, at most 500. Defaults to CALDAV_MAX_EVENTS.
after	string	no	The truncated.next_cursor of a previous call, to continue where it stopped. The window has to be the same one.

get_task

Read one task in full — read-only

The complete task behind an id from list_tasks, with its untruncated description and every reminder.

Parameter	Type	Required	Description
id	string	yes	An id from a listing tool. Not meant to be built by hand.

list_journals

List journal entries — read-only

Dated notes in a calendar, inside a time range. Most calendar clients hide these; a CalDAV server stores them alongside events and tasks, and some workflows use them as a diary.

Parameter	Type	Required	Description
from	string	no	ISO 8601: "2026-09-07" for a whole day, "2026-09-07T09:00:00" in the timezone argument or CALDAV_TIMEZONE, or "2026-09-07T09:00:00+02:00".
to	string	no	ISO 8601: "2026-09-07" for a whole day, "2026-09-07T09:00:00" in the timezone argument or CALDAV_TIMEZONE, or "2026-09-07T09:00:00+02:00".
timezone	string	no	IANA zone for timestamps that carry no offset, e.g. "Europe/Berlin". Defaults to CALDAV_TIMEZONE. Refused together with a value that already carries an offset.
calendars	string[]	no	Which calendars to look in. Leave it out for all of them. A calendar outside CALDAV_CALENDARS is refused rather than silently skipped.
limit	integer	no	Entries to return, at most 500. Defaults to CALDAV_MAX_EVENTS.
after	string	no	The truncated.next_cursor of a previous call, to continue where it stopped. The window has to be the same one.

get_journal

Read one journal entry in full — read-only

The complete note behind an id from list_journals, untruncated. This is the longest piece of somebody else’s prose this server hands over, so the text channel carries it inside an explicit untrusted fence.

Parameter	Type	Required	Description
id	string	yes	An id from a listing tool. Not meant to be built by hand.

Write tools

create_event

Create an event — write, essential

Adds an event to a calendar. The UID and the file name are generated here, so an existing entry can never be overwritten by accident. Times without an offset are read in the timezone argument or in CALDAV_TIMEZONE.

Parameter	Type	Required	Description
calendar_id	string	yes	A calendar id from list_calendars — its path. A full URL or the final path segment work too.
summary	string	yes	The title.
start	string	yes	When it starts. A bare date makes it an all-day event.
end	string	no	When it ends. For an all-day event this is exclusive, as iCalendar defines it: a single day ends on the following date. Defaults to one hour after the start, or one day for an all-day event.
timezone	string	no	IANA zone for timestamps that carry no offset, e.g. "Europe/Berlin". Defaults to CALDAV_TIMEZONE. Refused together with a value that already carries an offset.
description	unknown	no	Longer text. Pass null to remove it, leave it out to keep it.
location	unknown	no	Where it happens. Pass null to remove it, leave it out to keep it.
categories	unknown	no	Replaces every category. Pass null or an empty array to clear.
status	"CONFIRMED" | "TENTATIVE" | "CANCELLED"	no
transparent	boolean	no	True to leave the time free rather than marking it busy.
recurrence	string	no	A raw RRULE, e.g. "FREQ=WEEKLY;BYDAY=MO;COUNT=10". Given as written rather than as separate fields, because the rule grammar is richer than any short set of parameters, and a half-modelled rule is how a series ends up wrong.
alarms	object[]	no	Replaces the plain DISPLAY reminders. An empty array removes them. Reminders this server cannot write — email alarms, repeating ones, ones with an attachment — are always kept, and the answer says how many.

update_event 👤

Change an event — write, destructive, essential

Changes the fields named and leaves everything else exactly as it was — including properties this server does not model, attendees, attachments and reminders it cannot write. Pass null to clear a field. Guarded by the entry’s ETag: if it changed since it was read, nothing is written and the answer says what it is now. Changing a whole recurring series asks first.

Parameter	Type	Required	Description
id	string	yes	An id from a listing tool. Not meant to be built by hand.
scope	"this_occurrence" | "entire_series"	no	For a recurring entry: change just this occurrence, or the whole series. Defaults to whichever the id names. Changing a whole series asks first.
summary	string	no	The title.
start	string	no	ISO 8601: "2026-09-07" for a whole day, "2026-09-07T09:00:00" in the timezone argument or CALDAV_TIMEZONE, or "2026-09-07T09:00:00+02:00".
end	string	no	ISO 8601: "2026-09-07" for a whole day, "2026-09-07T09:00:00" in the timezone argument or CALDAV_TIMEZONE, or "2026-09-07T09:00:00+02:00".
timezone	string	no	IANA zone for timestamps that carry no offset, e.g. "Europe/Berlin". Defaults to CALDAV_TIMEZONE. Refused together with a value that already carries an offset.
description	unknown	no	Longer text. Pass null to remove it, leave it out to keep it.
location	unknown	no	Where it happens. Pass null to remove it, leave it out to keep it.
categories	unknown	no	Replaces every category. Pass null or an empty array to clear.
status	"CONFIRMED" | "TENTATIVE" | "CANCELLED"	no
transparent	boolean	no
alarms	object[]	no	Replaces the plain DISPLAY reminders. An empty array removes them. Reminders this server cannot write — email alarms, repeating ones, ones with an attachment — are always kept, and the answer says how many.
confirm_token	string	no	Token from the first call of this tool.

delete_event 👤

Delete an event — write, destructive

Removes an event. An occurrence id removes just that occurrence — which iCalendar does by adding an exception date to the series, so the rest of the series is untouched. A series id removes the whole entry. A CalDAV server keeps no history: this cannot be undone.

Parameter	Type	Required	Description
id	string	yes	An id from a listing tool. Not meant to be built by hand.
scope	"this_occurrence" | "entire_series"	no	For a recurring entry: change just this occurrence, or the whole series. Defaults to whichever the id names. Changing a whole series asks first.
confirm_token	string	no	Token from the first call of this tool.

move_event 👤

Move an event to another calendar — write, destructive

Copies an event into another calendar and removes it from the first. The content survives, the address does not: every id that named this event stops working, and a listing is needed to get the new one. The destination may be a calendar other people can see.

Parameter	Type	Required	Description
id	string	yes	An id from a listing tool. Not meant to be built by hand.
destination_calendar_id	string	yes	A calendar id from list_calendars — its path. A full URL or the final path segment work too.
confirm_token	string	no	Token from the first call of this tool.

respond_to_event 👤

Accept or decline an invitation — write

Sets your own participation status on an event you were invited to. On a server with scheduling enabled this sends a reply to the organiser, which cannot be unsent — so it asks first. It changes only your own attendee line and never anybody else’s. This server cannot add or remove attendees at all.

Parameter	Type	Required	Description
id	string	yes	An id from a listing tool. Not meant to be built by hand.
response	"ACCEPTED" | "DECLINED" | "TENTATIVE"	yes	Your answer.
confirm_token	string	no	Token from the first call of this tool.

create_task

Create a task — write

Adds a task to a calendar that accepts them. list_calendars reports which do — a collection created for events only will refuse a task, and this server checks before writing rather than passing the server’s refusal back.

Parameter	Type	Required	Description
calendar_id	string	yes	A calendar id from list_calendars — its path. A full URL or the final path segment work too.
summary	string	yes	The title.
due	string	no	When it is due.
start	string	no	When work on it can begin.
timezone	string	no	IANA zone for timestamps that carry no offset, e.g. "Europe/Berlin". Defaults to CALDAV_TIMEZONE. Refused together with a value that already carries an offset.
description	unknown	no	Longer text. Pass null to remove it, leave it out to keep it.
priority	integer	no	1 is highest, 9 lowest, 0 undefined — as RFC 5545 has it.
categories	unknown	no	Replaces every category. Pass null or an empty array to clear.
alarms	object[]	no	Replaces the plain DISPLAY reminders. An empty array removes them. Reminders this server cannot write — email alarms, repeating ones, ones with an attachment — are always kept, and the answer says how many.

update_task

Change a task — write, destructive

Changes the fields named and leaves everything else as it was. Pass null to clear a field. Guarded by the entry’s ETag. To mark a task done use complete_task, which records the completion time as well.

Parameter	Type	Required	Description
id	string	yes	An id from a listing tool. Not meant to be built by hand.
summary	string	no	The title.
due	string	no	ISO 8601: "2026-09-07" for a whole day, "2026-09-07T09:00:00" in the timezone argument or CALDAV_TIMEZONE, or "2026-09-07T09:00:00+02:00".
start	string	no	ISO 8601: "2026-09-07" for a whole day, "2026-09-07T09:00:00" in the timezone argument or CALDAV_TIMEZONE, or "2026-09-07T09:00:00+02:00".
timezone	string	no	IANA zone for timestamps that carry no offset, e.g. "Europe/Berlin". Defaults to CALDAV_TIMEZONE. Refused together with a value that already carries an offset.
description	unknown	no	Longer text. Pass null to remove it, leave it out to keep it.
priority	integer	no
percent_complete	integer	no
categories	unknown	no	Replaces every category. Pass null or an empty array to clear.
alarms	object[]	no	Replaces the plain DISPLAY reminders. An empty array removes them. Reminders this server cannot write — email alarms, repeating ones, ones with an attachment — are always kept, and the answer says how many.

complete_task

Mark a task done, or reopen it — write

Sets the task’s status. Marking it done records the completion time and sets it to 100 %; reopening clears both. The previous state is written down in the entry, so this is reversible — which is why it does not ask first.

Parameter	Type	Required	Description
id	string	yes	An id from a listing tool. Not meant to be built by hand.
done	boolean	no	Defaults to true. Pass false to reopen a completed task.

delete_task 👤

Delete a task — write, destructive

Removes a task. A CalDAV server keeps no history: this cannot be undone. To mark a task done instead, use complete_task.

Parameter	Type	Required	Description
id	string	yes	An id from a listing tool. Not meant to be built by hand.
confirm_token	string	no	Token from the first call of this tool.

create_journal

Create a journal entry — write

Adds a dated note to a calendar that accepts journal entries. list_calendars reports which do.

Parameter	Type	Required	Description
calendar_id	string	yes	A calendar id from list_calendars — its path. A full URL or the final path segment work too.
summary	string	yes	The heading.
date	string	yes	The date the note belongs to.
timezone	string	no	IANA zone for timestamps that carry no offset, e.g. "Europe/Berlin". Defaults to CALDAV_TIMEZONE. Refused together with a value that already carries an offset.
description	unknown	no	The note itself. Pass null to remove it, leave it out to keep it.
categories	unknown	no	Replaces every category. Pass null or an empty array to clear.

update_journal

Change a journal entry — write, destructive

Replaces the fields named. A CalDAV server keeps no version history, so the previous text of a note is gone once this succeeds — pass only the fields to change, and pass null to clear one. Guarded by the entry’s ETag, so a note changed elsewhere in the meantime is not silently overwritten.

Parameter	Type	Required	Description
id	string	yes	An id from a listing tool. Not meant to be built by hand.
summary	string	no	The title.
date	string	no	ISO 8601: "2026-09-07" for a whole day, "2026-09-07T09:00:00" in the timezone argument or CALDAV_TIMEZONE, or "2026-09-07T09:00:00+02:00".
timezone	string	no	IANA zone for timestamps that carry no offset, e.g. "Europe/Berlin". Defaults to CALDAV_TIMEZONE. Refused together with a value that already carries an offset.
description	unknown	no	The note itself. Pass null to remove it, leave it out to keep it.
categories	unknown	no	Replaces every category. Pass null or an empty array to clear.

delete_journal 👤

Delete a journal entry — write, destructive

Removes a dated note. A CalDAV server keeps no history, and a note is somebody’s writing: this cannot be undone.

Parameter	Type	Required	Description
id	string	yes	An id from a listing tool. Not meant to be built by hand.
confirm_token	string	no	Token from the first call of this tool.