Find a user by their email address.
AI agents call lookup_user_by_email to retrieve information from Slack MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs a lookup/query operation to retrieve user information based on an email address. It has no side effects, does not modify data, does not execute code or external operations, and does not involve financial transactions. It is a straightforward Read operation with minimal blast radius—an AI agent misusing this could only retrieve user profile information already accessible within the Slack workspace.
From the tool's definition Tool name 'lookup_user_by_email' and description 'Find a user by their email address' indicate a simple query operation that retrieves user information without modifying, deleting, or executing actions.
Attacks that exploit this kind of access
Find a user by their email address. It is categorised as a Read tool in the Slack MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Slack MCP Server MCP server in PolicyLayer and add a rule for lookup_user_by_email: 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 Slack MCP Server. Nothing to install.
lookup_user_by_email 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 lookup_user_by_email 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 lookup_user_by_email. 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.
lookup_user_by_email is provided by the Slack MCP Server MCP server (software-engineer-mj/slack-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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