AI agents call calendar_check_availability 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.
This tool checks calendar availability, which is a read-only operation that retrieves and queries existing calendar data without modifying, executing external code, or causing side effects. The empty description reduces confidence slightly, but the function name clearly indicates a non-mutating query operation typical of the 'Read' category.
From the tool's definition Tool name 'calendar_check_availability' indicates a query operation that retrieves calendar data to determine availability. No destructive, write, execute, or financial operations are suggested by the name.
Attacks that exploit this kind of access
calendar_check_availability. 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_check_availability: 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_check_availability 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_check_availability 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_check_availability. 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_check_availability 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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