feed_hold · Cnc Fluidnc MCP: Risk & Policy

WHAT IT DOES

What feed_hold does on Cnc Fluidnc

AI agents invoke feed_hold 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 feed_hold needs a policy

This tool sends a real-time command to a CNC machine to immediately pause motion. It is an Execute-category action because it triggers an external physical operation (halting machine movement). Severity is high because misuse on an actively cutting CNC router could cause material damage, tool breakage, or unsafe machine states, though it is safer than commands that start or resume motion.

From the tool's definition 'Pause machine motion immediately (feed hold)' - triggers an immediate external operation on physical CNC hardware

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

feed_hold Rate-limited

feed_hold 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": {
    "feed_hold": {
      "limits": [
        {
          "counter": "feed_hold_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 feed_hold

What does the feed_hold tool do? +

Pause machine motion immediately (feed hold). Sends. 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 feed_hold? +

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

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

Can I rate-limit feed_hold? +

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

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

feed_hold 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.