list_symbol_libraries

THE RISK

Low Risk

Why list_symbol_libraries needs a policy

This tool retrieves and enumerates symbol libraries from KiCAD's configuration without modifying, executing, or deleting anything. It is a pure read operation that simply exposes available library metadata. The blast radius of misuse is minimal—an attacker could discover which libraries are available, but cannot manipulate designs or execute code.

From the tool's definition Tool name 'list_symbol_libraries' and description 'List all available KiCAD symbol libraries' indicate a retrieval/query operation with no side effects.

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

POLICY

How to control list_symbol_libraries

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_symbol_libraries:

policy.json

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

list_symbol_libraries 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

Related tools and policies

More KiCAD-MCP-Server tools

Destructive delete_component Remove a component from the PCB by its reference designator. Destructive delete_schematic_component Remove a placed symbol from a KiCAD schematic (.kicad_sch). This removes the symbol insta Destructive delete_schematic_net_label Remove a net label from the schematic. Destructive delete_schematic_wire Remove a wire from the schematic by start and end coordinates. Destructive delete_symbol Remove a symbol from a .kicad_sym library file. Destructive delete_trace Delete traces from the PCB. Can delete by UUID, position, or bulk-delete all traces on a n Destructive remove_schematic_component_property Remove a single custom property from a placed schematic symbol. Built-in fields (Referenc Execute autoroute Run Freerouting autorouter on the current PCB. Exports to Specctra DSN, runs Freerouting C

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Read tools on other servers

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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_symbol_libraries

What does the list_symbol_libraries tool do? +

List all available KiCAD symbol libraries from global sym-lib-table, plus the project. 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_symbol_libraries? +

Register the KiCAD-MCP-Server MCP server in PolicyLayer and add a rule for list_symbol_libraries: 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_symbol_libraries? +

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

Can I rate-limit list_symbol_libraries? +

Yes. Add a rate_limit block to the list_symbol_libraries 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_symbol_libraries completely? +

Set action: deny in the PolicyLayer policy for list_symbol_libraries. 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_symbol_libraries? +

list_symbol_libraries 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 →