add_event · MCP Calendar Server MCP: Risk & Policy

WHAT IT DOES

What add_event does on MCP Calendar Server

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

WHY IT NEEDS A POLICY

Why add_event needs a policy

This tool creates new calendar events, which is a reversible write operation. While it modifies user data, the action can be undone by deleting the event. Severity is medium because calendar manipulation could cause scheduling conflicts or confusion, but lacks the irreversibility of destructive operations or financial impact. Confidence is high as the intent is explicit and unambiguous.

From the tool's definition Tool name is 'add_event' and description states 'Add a new event to user', indicating creation of new calendar data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add_event Rate-limited

add_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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "add_event": {
      "limits": [
        {
          "counter": "add_event_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches MCP Calendar Server, so you can run agents against it safely.

FAQ

Questions about add_event

What does the add_event tool do? +

Add a new event to user. It is categorised as a Write tool in the MCP Calendar Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on add_event? +

Register the MCP Calendar Server MCP server in PolicyLayer and add a rule for add_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 Calendar Server. Nothing to install.

What risk level is add_event? +

add_event is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit add_event? +

Yes. Add a rate_limit block to the add_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.

How do I block add_event completely? +

Set action: deny in the PolicyLayer policy for add_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.

What MCP server provides add_event? +

add_event is provided by the MCP Calendar Server MCP server (tekuor/mcp-calendar). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.