AI agents call users_priority_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 and ranks user contact data based on interaction metrics. It performs data retrieval without creating, modifying, deleting, or executing operations. However, the 'medium' severity reflects that contact frequency data could be sensitive information in a workspace context, and access to such ranked lists could reveal organizational communication patterns or relationships to an AI agent.
From the tool's definition Tool description states 'Get contacts ranked by interaction frequency' — a retrieval operation with no modification. The reference to 'undocumented session endpoint' suggests internal/private API use but does not change the read-only nature.
Attacks that exploit this kind of access
Get contacts ranked by interaction frequency (undocumented session endpoint). 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 users_priority_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.
users_priority_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 users_priority_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 users_priority_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.
users_priority_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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