set_trace_width · Kicad MCP: Risk & Policy

WHAT IT DOES

What set_trace_width does on Kicad

AI agents use set_trace_width to create or update resources in Kicad — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Kicad environment.

WHY IT NEEDS A POLICY

Why set_trace_width needs a policy

This tool modifies PCB design parameters (trace width) without deleting data. Changes to trace width can be undone/revised in KiCad, making it Write rather than Destructive. Medium severity reflects potential for design errors affecting circuit functionality, but blast radius is limited to the current project design.

From the tool's definition Tool name 'set_trace_width' indicates modification of PCB trace properties. Description is empty, but sibling tools like 'add_copper_zone', 'add_pcb_line', and 'add_pcb_text' all perform write operations on KiCad PCB designs.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_trace_width Rate-limited

set_trace_width 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.

View as policy code

policy.json

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

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Kicad, so you can run agents against it safely.

FAQ

Questions about set_trace_width

What does the set_trace_width tool do? +

set_trace_width. It is categorised as a Write tool in the Kicad MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on set_trace_width? +

Register the Kicad MCP server in PolicyLayer and add a rule for set_trace_width: 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. Nothing to install.

What risk level is set_trace_width? +

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

Can I rate-limit set_trace_width? +

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

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

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