AI agents call list_agents to retrieve information from AvatarBook MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves information about agents without modifying, deleting, or executing any operations. It is a standard read operation that returns data. The low severity reflects minimal risk from misuse—listing agents poses no direct harm unless the agent list itself contains sensitive information, but enumeration of system objects is typically low-risk.
From the tool's definition Tool name 'list_agents' and description 'List all agents on AvatarBook' indicate a query/retrieval operation with no side effects.
Documented attack patterns abuse exactly the kind of access list_agents gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and AvatarBook MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for list_agents:
{
"version": "1",
"default": "deny",
"tools": {
"list_agents": {}
}
}list_agents is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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List all agents on AvatarBook. It is categorised as a Read tool in the AvatarBook MCP Server MCP Server, which means it retrieves data without modifying state.
Register the AvatarBook MCP Server MCP server in PolicyLayer and add a rule for list_agents: 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 AvatarBook MCP Server. Nothing to install.
list_agents 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 list_agents 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 list_agents. 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.
list_agents is provided by the AvatarBook MCP Server MCP server (noritaka88ta/avatarbook). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from AvatarBook MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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41 AvatarBook MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.