# update_event

A write tool on the Calendar MCP server.

Agent View of the PolicyLayer registry record for `update_event`. HTML page: https://policylayer.com/tools/deciduus-calendar-mcp/update-event

## Facts

- Tool: `update_event`
- Server: Calendar (`deciduus/calendar-mcp`) — https://policylayer.com/tools/deciduus-calendar-mcp.md
- Homepage: https://github.com/deciduus/calendar-mcp
- Risk category: Write (Medium risk)
- Registry record: grade D, identity unverified
- Server rate-limited: no
- Parameters: 0
- Recommended policy verdict: Rate-limited

## Example call (MCP tools/call, JSON-RPC 2.0)

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "update_event",
    "arguments": {}
  }
}
```

## Why update_event is rated Medium

This tool modifies existing calendar events reversibly (updates are not permanent deletions and can be undone by further updates). While the description is empty, the context of a calendar server and the naming convention clearly indicates write operations. Severity is medium because calendar event modifications have limited blast radius—they affect scheduling but not financial transactions or data destruction.

From the tool's own definition: "Tool name is 'update_event' on a calendar MCP server with sibling tools like 'create_event' and 'delete_event'. The 'update_' prefix indicates modification of existing calendar data."

## Use case

AI agents use update_event to create or update resources in Calendar, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Calendar environment.

## Recommended policy (PolicyLayer)

Verdict: **Rate-limited**. Enforced by the PolicyLayer MCP gateway (https://policylayer.com/mcp-gateway) before a call reaches Calendar:

```json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "update_event": {
      "limits": [
        {
          "counter": "update_event_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}
```

## Other tools on Calendar (11)

- `delete_event` — Destructive — https://policylayer.com/tools/deciduus-calendar-mcp/delete-event.md
- `analyze_busyness` — Read — https://policylayer.com/tools/deciduus-calendar-mcp/analyze-busyness.md
- `check_attendee_status` — Read — https://policylayer.com/tools/deciduus-calendar-mcp/check-attendee-status.md
- `find_events` — Read — https://policylayer.com/tools/deciduus-calendar-mcp/find-events.md
- `list_calendars` — Read — https://policylayer.com/tools/deciduus-calendar-mcp/list-calendars.md
- `query_free_busy` — Read — https://policylayer.com/tools/deciduus-calendar-mcp/query-free-busy.md
- `add_attendee` — Write — https://policylayer.com/tools/deciduus-calendar-mcp/add-attendee.md
- `create_calendar` — Write — https://policylayer.com/tools/deciduus-calendar-mcp/create-calendar.md
- `create_event` — Write — https://policylayer.com/tools/deciduus-calendar-mcp/create-event.md
- `quick_add_event` — Write — https://policylayer.com/tools/deciduus-calendar-mcp/quick-add-event.md
- `schedule_mutual` — Write — https://policylayer.com/tools/deciduus-calendar-mcp/schedule-mutual.md

## For agents

This record is a snapshot. Live verdicts and the full registry:

- Check every server in your MCP config at once: `npx -y policylayer stack`
- Vet a server before you add it: install the mcp-precheck skill — `npx skills add https://policylayer.com` (skill text: https://policylayer.com/skill.md)
- Query the registry over MCP: endpoint `https://api.policylayer.com/mcp` — tools `check_mcp_server`, `check_mcp_stack`, `check_tool`, `search_registry`, `get_change_events`

---

Source: the PolicyLayer MCP registry — one continuously verified record per MCP server. Full record: https://policylayer.com/registry?q=deciduus-calendar-mcp · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/deciduus-calendar-mcp