List available expert types that can be created with create_expert
AI agents call list_experts to retrieve information from Nexus Agents without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This is a read-only operation that queries and returns information about available expert types. It performs no modifications, executions, deletions, or financial transactions. The tool merely enumerates existing expert configurations, making it a straightforward Read category with low severity and blast radius.
From the tool's definition Tool name is 'list_experts' and description states it 'List available expert types' — a retrieval operation with no side effects.
Documented attack patterns abuse exactly the kind of access list_experts gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Nexus Agents, and nothing reaches the server without passing your rules. This is the rule we recommend for list_experts:
{
"version": "1",
"default": "deny",
"tools": {
"list_experts": {}
}
}list_experts is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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List available expert types that can be created with create_expert. It is categorised as a Read tool in the Nexus Agents MCP Server, which means it retrieves data without modifying state.
Register the Nexus Agents MCP server in PolicyLayer and add a rule for list_experts: 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 Nexus Agents. Nothing to install.
list_experts 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_experts 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_experts. 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_experts is provided by the Nexus Agents MCP server (nexus-substrate/nexus-agents). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Nexus Agents, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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9 Nexus Agents tools catalogued and risk-classified — across an index of 43,000+ MCP servers.