AI agents call search_users_for_mentions to retrieve information from Teams without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool queries a directory or user database to find and display user information for the purpose of constructing mentions in messages. It performs a read-only lookup operation with no capability to create, modify, delete, or execute actions. The returned data (display names, emails, mention IDs) is informational only.
From the tool's definition Tool description states it 'Search for users' and 'Returns users with their display names, email addresses, and mention IDs.' The verb 'search' and 'returns' indicate data retrieval with no modification or side effects.
Attacks that exploit this kind of access
Search for users to mention in messages. Returns users with their display names, email addresses, and mention IDs. It is categorised as a Read tool in the Teams MCP Server, which means it retrieves data without modifying state.
Register the Teams MCP server in PolicyLayer and add a rule for search_users_for_mentions: 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 Teams. Nothing to install.
search_users_for_mentions 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 search_users_for_mentions 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 search_users_for_mentions. 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.
search_users_for_mentions is provided by the Teams MCP server (@floriscornel/teams-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.