add_pcb_line · Kicad MCP: Risk & Policy

WHAT IT DOES

What add_pcb_line does on Kicad

AI agents use add_pcb_line 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 add_pcb_line needs a policy

This tool creates new PCB graphic elements (lines) on specified layers. It modifies the PCB design reversibly—lines can be deleted or edited—making it a Write operation rather than Destructive. The change affects the physical design output but is not a deletion or irreversible operation.

From the tool's definition Tool name 'add_pcb_line' and description explicitly state it 'Add[s] a graphic line to the PCB'. This is a create operation that modifies PCB design data. The mention of 'edge cuts, silkscreen, etc.' indicates it writes to specific PCB layers.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add_pcb_line Rate-limited

add_pcb_line 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": {
    "add_pcb_line": {
      "limits": [
        {
          "counter": "add_pcb_line_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 add_pcb_line

What does the add_pcb_line tool do? +

Add a graphic line to the PCB (edge cuts, silkscreen, etc.). 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 add_pcb_line? +

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

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

Can I rate-limit add_pcb_line? +

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

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

add_pcb_line 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.