set_net_class · Kicad MCP: Risk & Policy

WHAT IT DOES

What set_net_class does on Kicad

AI agents use set_net_class 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_net_class needs a policy

Net classes in KiCad define electrical properties (trace width, clearance, via size) for groups of nets. Setting a net class modifies design parameters reversibly but with potentially significant consequences—incorrect net class assignments could cause electrical rule violations, manufacturing issues, or signal integrity problems.

From the tool's definition Tool name 'set_net_class' in KiCad PCB/schematic design context. Sibling tools include 'add_copper_zone', 'add_global_label', 'add_hierarchical_sheet', 'add_lib_symbol', 'add_pcb_line', 'add_pcb_text'—all Write operations that modify design.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_net_class Rate-limited

set_net_class 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_net_class": {
      "limits": [
        {
          "counter": "set_net_class_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_net_class

What does the set_net_class tool do? +

set_net_class. 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_net_class? +

Register the Kicad MCP server in PolicyLayer and add a rule for set_net_class: 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_net_class? +

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

Can I rate-limit set_net_class? +

Yes. Add a rate_limit block to the set_net_class 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_net_class completely? +

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

set_net_class 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.