> ## Documentation Index
> Fetch the complete documentation index at: https://docs.langmail.me/llms.txt
> Use this file to discover all available pages before exploring further.

# update_calendar_event

> Replace an existing event in place — identified by its uid — and re-send iMIP notifications to attendees.

Updates an event as a **full replacement**: pass the complete event details, not just the changed fields. Attendees are re-notified automatically.

For a recurring event, this edits the **entire series**. Pass `recurrence` again to keep it recurring — omitting it collapses the series back to a single event. Editing one occurrence of a series (`RECURRENCE-ID`) is not supported.

## Parameters

All parameters of [`create_calendar_event`](/reference/mcp/create-calendar-event), plus:

<ParamField body="uid" type="string" required>
  The event's iCalendar UID, from `create_calendar_event` or [`list_calendar_events`](/reference/mcp/list-calendar-events). Up to 255 characters; must not contain path separators.
</ParamField>

## Example

```json Call theme={null}
{
  "uid": "9b1de2a4-6f0e-4c8b-a1d2-3e4f5a6b7c8d@langmail.me",
  "title": "Review",
  "start": "2026-07-15T14:00:00+02:00",
  "end": "2026-07-15T14:45:00+02:00",
  "attendees": ["anna@example.com"]
}
```

```text Result theme={null}
Event "Review" updated and notifications sent to 1 attendee(s): anna@example.com.
```

## Errors

* `Event not found: <uid>` — no event with that UID in the target calendar.
* `Event end must be after its start.`
* `Calendar not found: <url>` — the `calendarUrl` didn't resolve.