AI agents call get-active-users to retrieve information from Liveblocks without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves active user information from a Liveblocks room, which is a read-only query operation with no side effects. The blast radius of misuse is minimal—an attacker could enumerate active users but cannot modify, delete, or execute external actions. Classified as Read with low severity.
From the tool's definition Tool name 'get-active-users' and description 'Get a Liveblocks room' indicate retrieval of room data without modification. No creation, deletion, or execution of external operations.
Documented attack patterns abuse exactly the kind of access get-active-users gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Liveblocks, and nothing reaches the server without passing your rules. This is the rule we recommend for get-active-users:
{
"version": "1",
"default": "deny",
"tools": {
"get-active-users": {}
}
}get-active-users is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get a Liveblocks room. It is categorised as a Read tool in the Liveblocks MCP Server, which means it retrieves data without modifying state.
Register the Liveblocks MCP server in PolicyLayer and add a rule for get-active-users: 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 Liveblocks. Nothing to install.
get-active-users 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 get-active-users 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 get-active-users. 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.
get-active-users is provided by the Liveblocks MCP server (liveblocks/liveblocks-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Liveblocks, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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39 Liveblocks tools catalogued and risk-classified — across an index of 43,000+ MCP servers.