AI agents call usergroups_list to retrieve information from Slack without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves user group information from Slack without modifying data. However, user groups can include sensitive organizational structure and membership information, which elevates severity from 'low' to 'medium' due to potential information disclosure risks if misused by an AI agent to map organizational hierarchies or identify specific users.
From the tool's definition Tool name 'usergroups_list' indicates a listing/query operation. The broader server description mentions 'Slack: messages, channels, files, canvases, lists, search, reactions, and more' where 'lists' and 'search' are explicitly Read operations.
Attacks that exploit this kind of access
usergroups_list. It is categorised as a Read tool in the Slack MCP Server, which means it retrieves data without modifying state.
Register the Slack MCP server in PolicyLayer and add a rule for usergroups_list: 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. Nothing to install.
usergroups_list 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 usergroups_list 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 usergroups_list. 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.
usergroups_list is provided by the Slack MCP server (karbassi/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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