// MCP TOOL REFERENCE

refill_zones

Refill all copper zones on the board. WARNING: SWIG path has known segfault risk (see KNOWN_ISSUES.md). Prefer using IPC backend (KiCAD open) or triggering zone fill via KiCAD UI instead.

ServerKiCAD-MCP-Server
CategoryExecute

How to control refill_zones ↓

WHAT IT DOES

What refill_zones does on KiCAD-MCP-Server

AI agents invoke refill_zones to trigger actions in KiCAD-MCP-Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

THE RISK

High Risk

Why refill_zones needs a policy

This tool triggers a board-level operation (refilling copper zones) which modifies the PCB design state. It is an Execute-class action as it runs an external operation with side effects on the KiCAD board file. The severity is high because misuse or crashes (noted segfault risk) could corrupt the board design, and the operation affects all copper zones globally across the board.

From the tool's definition 'Refill all copper zones on the board' and 'WARNING: SWIG path has known segfault risk (see KNOWN_ISSUES.md)'

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

POLICY

How to control refill_zones

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 refill_zones:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "refill_zones": {
      "limits": [
        {
          "counter": "refill_zones_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

refill_zones stays usable, but rate-capped — a runaway agent can't fire it dozens of times 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.

RATE-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

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Go deeper

High-risk tools in KiCAD-MCP-Server → Every high-risk tool this server exposes, in one view.
All high-risk MCP tools → Every high-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about refill_zones

What does the refill_zones tool do? +

Refill all copper zones on the board. WARNING: SWIG path has known segfault risk (see KNOWN_ISSUES.md). Prefer using IPC backend (KiCAD open) or triggering zone fill via KiCAD UI instead. It is categorised as a Execute tool in the KiCAD-MCP-Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on refill_zones? +

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

refill_zones is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit refill_zones? +

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

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

refill_zones 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 →

Free to start. No card required.

157 KiCAD-MCP-Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.