list_calendar_events

THE RISK

Low Risk

Why list_calendar_events needs a policy

This tool retrieves and queries calendar event data without modifying, deleting, or executing any operations. It is a straightforward read operation that poses minimal security risk as it only exposes existing calendar information to the AI agent.

From the tool's definition Tool name is 'list_calendar_events' and description states 'List events from a calendar' - this is a retrieval operation with no side effects. No modification, deletion, execution, or financial transaction is performed.

Documented attack patterns abuse exactly the kind of access list_calendar_events gives an agent:

POLICY

How to control list_calendar_events

PolicyLayer is an MCP gateway — it sits between your AI agents and Fastmail MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for list_calendar_events:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "list_calendar_events": {}
  }
}

list_calendar_events is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register Fastmail MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

CAP THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about list_calendar_events

What does the list_calendar_events tool do? +

List events from a calendar. It is categorised as a Read tool in the Fastmail MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on list_calendar_events? +

Register the Fastmail MCP Server MCP server in PolicyLayer and add a rule for list_calendar_events: 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 Fastmail MCP Server. Nothing to install.

What risk level is list_calendar_events? +

list_calendar_events is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit list_calendar_events? +

Yes. Add a rate_limit block to the list_calendar_events 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 list_calendar_events completely? +

Set action: deny in the PolicyLayer policy for list_calendar_events. 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 list_calendar_events? +

list_calendar_events is provided by the Fastmail MCP Server MCP server (madllama25/fastmail-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Fastmail MCP Server tool call.

Start from Fastmail MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →