calendar_list_calendars

THE RISK

Low Risk

Why calendar_list_calendars needs a policy

This tool retrieves calendar metadata without modifying it. While it exposes calendar information that may contain sensitive scheduling details, it is fundamentally a read operation. Severity is medium because calendar data can reveal personal/organizational patterns, but there is no data loss, execution, or financial impact.

From the tool's definition Tool name is 'calendar_list_calendars' and description states 'List all calendars accessible to the user.' The action is listing/querying data with no modification or side effects.

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

POLICY

How to control calendar_list_calendars

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

policy.json

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

calendar_list_calendars 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 Google Workspace — 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 →

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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 calendar_list_calendars

What does the calendar_list_calendars tool do? +

List all calendars accessible to the user. Args: - response_format (. It is categorised as a Read tool in the Google Workspace MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on calendar_list_calendars? +

Register the Google Workspace MCP server in PolicyLayer and add a rule for calendar_list_calendars: 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 Google Workspace. Nothing to install.

What risk level is calendar_list_calendars? +

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

Can I rate-limit calendar_list_calendars? +

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

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

calendar_list_calendars is provided by the Google Workspace MCP server (everyinc/google-workspace-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Google Workspace tool call.

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

CHECK YOUR STACK →