register_footprint_library

THE RISK

Medium Risk

Why register_footprint_library needs a policy

Registering a library is a configuration write operation that modifies KiCAD's library settings reversibly. It creates or updates a library reference without deleting data or executing arbitrary code. This is a standard library management operation with limited blast radius—incorrect registration can be corrected by re-registering or removing the entry.

From the tool's definition Tool name 'register_footprint_library' and description 'Register a .pretty footprint library in KiCAD' indicate adding/modifying a configuration entry for a footprint library resource.

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

POLICY

How to control register_footprint_library

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 register_footprint_library:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "register_footprint_library": {
      "limits": [
        {
          "counter": "register_footprint_library_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

register_footprint_library stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. 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.

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EXPLORE

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Write 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.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about register_footprint_library

What does the register_footprint_library tool do? +

Register a .pretty footprint library in KiCAD. It is categorised as a Write tool in the KiCAD-MCP-Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on register_footprint_library? +

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

register_footprint_library is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit register_footprint_library? +

Yes. Add a rate_limit block to the register_footprint_library 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 register_footprint_library completely? +

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

register_footprint_library 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 →