set_active_layer

THE RISK

Medium Risk

Why set_active_layer needs a policy

This tool modifies application state (active layer selection) which affects subsequent operations and is reversible—users can switch to a different layer. It does not execute arbitrary commands, delete data, or cause financial impact.

From the tool's definition Tool sets/modifies the active PCB layer state by name (e.g. 'F.Cu, B.Cu'), which changes the current editing context in KiCAD but does not delete or irreversibly destroy data.

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

POLICY

How to control set_active_layer

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 set_active_layer:

policy.json

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

set_active_layer 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.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More KiCAD-MCP-Server tools

Destructive delete_component Remove a component from the PCB by its reference designator. Destructive delete_schematic_component Remove a placed symbol from a KiCAD schematic (.kicad_sch). This removes the symbol insta Destructive delete_schematic_net_label Remove a net label from the schematic. Destructive delete_schematic_wire Remove a wire from the schematic by start and end coordinates. Destructive delete_symbol Remove a symbol from a .kicad_sym library file. Destructive delete_trace Delete traces from the PCB. Can delete by UUID, position, or bulk-delete all traces on a n Destructive remove_schematic_component_property Remove a single custom property from a placed schematic symbol. Built-in fields (Referenc Execute autoroute Run Freerouting autorouter on the current PCB. Exports to Specctra DSN, runs Freerouting C

All 157 KiCAD-MCP-Server tools →

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 set_active_layer

What does the set_active_layer tool do? +

Set the currently active PCB layer by name (e.g. F.Cu, B.Cu). 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 set_active_layer? +

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

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

Can I rate-limit set_active_layer? +

Yes. Add a rate_limit block to the set_active_layer 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_active_layer completely? +

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

set_active_layer 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 →