AI agents call list_connectors to retrieve information from NIST MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs a query/enumeration function that retrieves and displays information about registered connectors without creating, modifying, deleting, or executing any operations. The lack of parameters and the passive retrieval nature classify it as a Read operation with low severity since connector metadata exposure alone poses minimal direct risk in the context of a NIST compliance framework server.
From the tool's definition Tool name 'list_connectors' and description 'List all registered connectors' indicate a retrieval operation with no modifications or side effects.
Documented attack patterns abuse exactly the kind of access list_connectors gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and NIST MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for list_connectors:
{
"version": "1",
"default": "deny",
"tools": {
"list_connectors": {}
}
}list_connectors 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 registered connectors. It is categorised as a Read tool in the NIST MCP Server MCP Server, which means it retrieves data without modifying state.
Register the NIST MCP Server MCP server in PolicyLayer and add a rule for list_connectors: 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 NIST MCP Server. Nothing to install.
list_connectors 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_connectors 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_connectors. 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_connectors is provided by the NIST MCP Server MCP server (tnicholson/nist-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from NIST 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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44 NIST MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.