add_via · Kicad MCP: Risk & Policy

WHAT IT DOES

What add_via does on Kicad

AI agents use add_via 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_via needs a policy

The tool creates a new via on the PCB, which is a design element that can be added, modified, or removed. This falls under Write category as it modifies the PCB design reversibly. Severity is medium because incorrect via placement could impact PCB manufacturability and signal integrity, but the change can be undone.

From the tool's definition Tool name 'add_via' and description 'Add a via at a position' indicate creation of a physical design element (via) in a PCB layout. This is a reversible modification to the PCB design.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add_via Rate-limited

add_via 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_via": {
      "limits": [
        {
          "counter": "add_via_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_via

What does the add_via tool do? +

Add a via at a position. 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_via? +

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

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

Can I rate-limit add_via? +

Yes. Add a rate_limit block to the add_via 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_via completely? +

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

add_via 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.