soft_reset · Cnc Fluidnc MCP: Risk & Policy

WHAT IT DOES

What soft_reset does on Cnc Fluidnc

AI agents invoke soft_reset 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 soft_reset needs a policy

A soft reset of a CNC controller immediately halts all motion and spindle operation. While it doesn't permanently delete data, it triggers a critical external hardware operation that abruptly stops physical machinery. This falls under Execute (triggering external operations) with critical severity because misuse during active machining could damage workpieces, tooling, or cause safety hazards.

From the tool's definition Emergency stop — soft reset the controller (0x18). Stops all motion and spindle immediately. Requires confirm=true.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

soft_reset Rate-limited

soft_reset 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": {
    "soft_reset": {
      "limits": [
        {
          "counter": "soft_reset_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 soft_reset

What does the soft_reset tool do? +

Emergency stop — soft reset the controller (0x18). Stops all motion and spindle immediately. 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 soft_reset? +

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

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

Can I rate-limit soft_reset? +

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

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

soft_reset 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.