List all calendars visible to Hermes (own calendar + any shared with Hermes).
AI agents call cal_list_calendars to retrieve information from Hermes Google without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool only lists/retrieves calendar information with no side effects or data modification. It is a straightforward read operation with minimal risk—the worst case is information disclosure about which calendars are accessible. The narrow scope (calendars only, not event details) and non-destructive nature justify 'low' severity.
From the tool's definition Tool name 'cal_list_calendars' and description 'List all calendars visible to Hermes' indicate a query operation that retrieves calendar metadata without modification.
Attacks that exploit this kind of access
List all calendars visible to Hermes (own calendar + any shared with Hermes). It is categorised as a Read tool in the Hermes Google MCP Server, which means it retrieves data without modifying state.
Register the Hermes Google MCP server in PolicyLayer and add a rule for cal_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 Hermes Google. Nothing to install.
cal_list_calendars is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the cal_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.
Set action: deny in the PolicyLayer policy for cal_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.
cal_list_calendars is provided by the Hermes Google MCP server (jimmy-larsson/hermes-google). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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