AI agents call free_busy to retrieve information from Calendar without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves calendar availability information (free/busy status) for a specified time period. It performs no modifications, deletions, or external operations—it simply queries and returns existing calendar data. This is a classic Read operation with minimal security risk.
From the tool's definition Tool name 'free_busy' and description 'Get a free/busy summary for the next N days' indicate a query/retrieval operation that returns schedule availability data without modifying or deleting anything.
Attacks that exploit this kind of access
Get a free/busy summary for the next N days. It is categorised as a Read tool in the Calendar MCP Server, which means it retrieves data without modifying state.
Register the Calendar MCP server in PolicyLayer and add a rule for free_busy: 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 Calendar. Nothing to install.
free_busy 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 free_busy 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 free_busy. 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.
free_busy is provided by the Calendar MCP server (p-w-4-z/calendar-mcp). 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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