spindle_control · Cnc Fluidnc MCP: Risk & Policy

WHAT IT DOES

What spindle_control does on Cnc Fluidnc

AI agents invoke spindle_control to trigger actions in Cnc Fluidnc. 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.

WHY IT NEEDS A POLICY

Why spindle_control needs a policy

Activating a CNC spindle motor is a physical, real-world operation with serious safety implications — a spinning router/mill bit can cause injury, damage workpieces, or destroy tooling if activated unexpectedly. This is an Execute-category action (triggers external physical operation) with critical severity due to the potential for physical harm, fire, or machine damage if misused by an AI agent.

From the tool's definition Control the spindle: turn on (CW/CCW with speed) or off. Turning on requires confirm=true.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

spindle_control Rate-limited

spindle_control 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.

View as policy code

policy.json

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

RATE-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 spindle_control

What does the spindle_control tool do? +

Control the spindle: turn on (CW/CCW with speed) or off. Turning on requires confirm=true. It is categorised as a Execute tool in the Cnc Fluidnc MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on spindle_control? +

Register the Cnc Fluidnc MCP server in PolicyLayer and add a rule for spindle_control: 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 spindle_control? +

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

Can I rate-limit spindle_control? +

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

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

spindle_control 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.