This record as markdown: /tools/karbassi-slack-mcp/usergroups-users-update.md
What usergroups_users_update does on Slack
AI agents use usergroups_users_update to create or update resources in Slack, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Slack environment.
Why usergroups_users_update is rated Medium
The tool performs a reversible modification action (updating user group memberships) rather than deletion or execution of arbitrary code. This qualifies as Write category. Severity is high because modifying user group memberships can affect access controls, permissions, and organizational structure in Slack, with potential impact on collaboration and security boundaries.
From the tool's definition Tool name 'usergroups_users_update' indicates modification of user group membership. The verb 'update' combined with 'usergroups_users' strongly suggests writing/modifying group membership data. Description is empty, reducing confidence slightly.
Attacks that exploit this kind of access
The rule that runs usergroups_users_update safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Slack, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For usergroups_users_update, this is the rule to start with:
usergroups_users_update stays usable, but capped: an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Slack, apply this rule, and every usergroups_users_update call is checked against it from then on.
Questions about usergroups_users_update
usergroups_users_update is a write tool on the Slack MCP server. It is categorised as a Write tool in the Slack MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Slack MCP server in PolicyLayer and add a rule for usergroups_users_update: 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_users_update is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the usergroups_users_update 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_users_update. 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_users_update 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.
More on Slack, and thousands of servers like it.
This server
Across the catalogue