create_acl_rule · Gcalendar MCP: Risk & Policy

WHAT IT DOES

What create_acl_rule does on Gcalendar

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

WHY IT NEEDS A POLICY

Why create_acl_rule needs a policy

This tool creates new sharing permissions without permanently deleting or destroying data. It is reversible (the accompanying 'delete_acl_rule' tool confirms this). While sharing does expose calendar data to additional users, the primary action is creating/modifying ACL rules (Write category), not reading data. It does not execute arbitrary code, move money, or irreversibly delete data.

From the tool's definition Tool description states 'Share a calendar with someone,' which creates a new access control rule (ACL) that grants permissions to another user. This modifies calendar sharing settings, which is a reversible write operation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_acl_rule Rate-limited

create_acl_rule 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": {
    "create_acl_rule": {
      "limits": [
        {
          "counter": "create_acl_rule_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 Gcalendar, so you can run agents against it safely.

FAQ

Questions about create_acl_rule

What does the create_acl_rule tool do? +

Share a calendar with someone. It is categorised as a Write tool in the Gcalendar MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on create_acl_rule? +

Register the Gcalendar MCP server in PolicyLayer and add a rule for create_acl_rule: 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 Gcalendar. Nothing to install.

What risk level is create_acl_rule? +

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

Can I rate-limit create_acl_rule? +

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

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

create_acl_rule is provided by the Gcalendar MCP server (sandeepmallareddy/gcalendar-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.