list_tool_categories

THE RISK

Low Risk

Why list_tool_categories needs a policy

This tool performs information retrieval only—it returns metadata about available tool categories and their descriptions. There are no side effects, no data modifications, no code execution, and no destructive operations. It is purely a Read category tool with low severity since misuse would only expose internal tool availability information.

From the tool's definition Tool name 'list_tool_categories' and description 'List all available KiCAD tool categories' indicates a query/discovery operation that retrieves metadata about available tools without modifying or executing anything.

Documented attack patterns abuse exactly the kind of access list_tool_categories gives an agent:

POLICY

How to control list_tool_categories

PolicyLayer is an MCP gateway — it sits between your AI agents and KiCAD-MCP-Server, and nothing reaches the server without passing your rules. This is the rule we recommend for list_tool_categories:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "list_tool_categories": {}
  }
}

list_tool_categories is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register KiCAD-MCP-Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

CAP THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about list_tool_categories

What does the list_tool_categories tool do? +

List all available KiCAD tool categories with their descriptions and tool counts. Use this to discover which tools are available via the router. It is categorised as a Read tool in the KiCAD-MCP-Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on list_tool_categories? +

Register the KiCAD-MCP-Server MCP server in PolicyLayer and add a rule for list_tool_categories: 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 KiCAD-MCP-Server. Nothing to install.

What risk level is list_tool_categories? +

list_tool_categories is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit list_tool_categories? +

Yes. Add a rate_limit block to the list_tool_categories 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.

How do I block list_tool_categories completely? +

Set action: deny in the PolicyLayer policy for list_tool_categories. 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.

What MCP server provides list_tool_categories? +

list_tool_categories is provided by the KiCAD-MCP-Server MCP server (mixelpixx/kicad-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every KiCAD-MCP-Server tool call.

Start from KiCAD-MCP-Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →