AI agents call calendar_get_free_busy to retrieve information from M365 without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The tool retrieves free/busy information from a calendar—a read-only query operation with no side effects. Even if misused by an AI agent, it only exposes scheduling availability data without creating, modifying, or deleting records. Low severity due to limited blast radius; the information exposed is typically semi-sensitive but not financial or destructive.
From the tool's definition Tool name 'calendar_get_free_busy' indicates retrieval of calendar availability data. The description is empty, but context from sibling tools (calendar_check_availability, calendar_create_calendar) and the server's role managing Outlook and Calendar services…
Attacks that exploit this kind of access
calendar_get_free_busy. It is categorised as a Read tool in the M365 MCP Server, which means it retrieves data without modifying state.
Register the M365 MCP server in PolicyLayer and add a rule for calendar_get_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 M365. Nothing to install.
calendar_get_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 calendar_get_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 calendar_get_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.
calendar_get_free_busy is provided by the M365 MCP server (robin-collins/m365-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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