ListCalendarsTool

Lists the device's calendars via ContentResolver on CalendarContract.Calendars, so a model can pass a calendar_id to create_event. Requires READ_CALENDAR. Output: calendars (list of {id, name, account_name, account_type, color, writable, visible, is_default}) and count. writable means at least contributor access; is_default marks the calendar create_event uses when calendar_id is omitted (CalendarSupport.findWritableCalendarId). color is #RRGGBB. Param writable_only (default false) drops read-only calendars such as holidays and birthdays.