set_zero · Cnc Fluidnc MCP: Risk & Policy

WHAT IT DOES

What set_zero does on Cnc Fluidnc

AI agents use set_zero to create or update resources in Cnc Fluidnc — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Cnc Fluidnc environment.

WHY IT NEEDS A POLICY

Why set_zero needs a policy

This tool modifies the machine's work coordinate system (WCS) by executing G10 L20 P1, which redefines the zero reference point for the CNC machine. This is a reversible write operation (the coordinate system can be reset), but misuse could cause the machine to execute subsequent movements relative to a wrong origin, potentially leading to crashes, ruined workpieces, or machine damage. Hence severity is high.

From the tool's definition Set the work coordinate zero for specified axes at the current position (G10 L20 P1). If no axes specified, sets all axes to zero.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_zero Rate-limited

set_zero 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_zero": {
      "limits": [
        {
          "counter": "set_zero_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 Cnc Fluidnc, so you can run agents against it safely.

FAQ

Questions about set_zero

What does the set_zero tool do? +

Set the work coordinate zero for specified axes at the current position (G10 L20 P1). If no axes specified, sets all axes to zero. It is categorised as a Write tool in the Cnc Fluidnc 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_zero? +

Register the Cnc Fluidnc MCP server in PolicyLayer and add a rule for set_zero: 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 Cnc Fluidnc. Nothing to install.

What risk level is set_zero? +

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

Can I rate-limit set_zero? +

Yes. Add a rate_limit block to the set_zero 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_zero completely? +

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

set_zero is provided by the Cnc Fluidnc MCP server (whitneydesignlabs/cnc-fluidnc-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.