Update an existing calendar event. Before using this tool, make sure to: 1. Ask the user which fields they want to update 2. If moving to a different calendar, verify the calendar exists using calendars://list 3. If updating time, confirm the new time with the user 4. Ask if they want to add/upda...
AI agents use update_event to create or update resources in MCP iCal Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your MCP iCal Server environment.
This tool modifies existing calendar data reversibly. Users can change event details, and these modifications can be undone by updating the event again. It does not delete data (which would be Destructive), execute arbitrary code (Execute), or move money (Financial).
From the tool's definition Tool description states 'Update an existing calendar event' with optional parameters for title, start_time, location, notes, and reminders. The word 'update' and the optional modification of event fields are characteristic of Write operations.
Risk signalsBulk/mass operation — affects multiple targets
Documented attack patterns abuse exactly the kind of access update_event gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and MCP iCal Server, and nothing reaches the server without passing your rules. This is the rule we recommend for update_event:
{
"version": "1",
"default": "deny",
"tools": {
"update_event": {
"limits": [
{
"counter": "update_event_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}update_event stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
Free to start. No card required.
Update an existing calendar event. Before using this tool, make sure to: 1. Ask the user which fields they want to update 2. If moving to a different calendar, verify the calendar exists using calendars://list 3. If updating time, confirm the new time with the user 4. Ask if they want to add/update location if not specified 5. Ask if they want to add/update notes if not specified 6. Ask if they want to set reminders for the event Args: event_id: Unique identifier of the event to update title: Optional new title start_time: Optional new start time in ISO format end_time: Optional new end time in ISO format notes: Optional new notes/description. Ask user if they want to update notes. location: Optional new location. Ask user if they want to specify/update location. calendar_name: Optional new calendar. Ask user which calendar to use, referencing calendars://list. all_day: Optional all-day flag reminder_offsets: List of minutes before the event to trigger reminders\ e.g. [60, 1440] means two reminders, the first 24 hours before the event and the second one hour before. recurrence_rule: Optional recurrence rule for the event. This should be an instance of RecurrenceRule with the following fields: - frequency: Frequency of the recurrence (e.g., DAILY, WEEKLY, MONTHLY, YEARLY). - interval: Interval between recurrences (e.g., every 2 weeks). - end_date: Optional end date for the recurrence. If specified, the recurrence will stop on this date. - occurrence_count: Optional number of occurrences. If specified, the recurrence will stop after this many occurrences. - days_of_week: Optional list of weekdays for the event. Use integers to represent days: - Sunday: 1 - Monday: 2 - Tuesday: 3 - Wednesday: 4 - Thursday: 5 - Friday: 6 - Saturday: 7 Note: Both end_date and occurrence_count should not be set simultaneously; choose one or the other, or leave both unset. It is categorised as a Write tool in the MCP iCal Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the MCP iCal Server MCP server in PolicyLayer and add a rule for update_event: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches MCP iCal Server. Nothing to install.
update_event is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the update_event rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for update_event. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
update_event is provided by the MCP iCal Server MCP server (omar-v2/mcp-ical). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 4 MCP iCal Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
4 MCP iCal Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.