run_sd_file · Cnc Fluidnc MCP: Risk & Policy

WHAT IT DOES

What run_sd_file does on Cnc Fluidnc

AI agents invoke run_sd_file 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 run_sd_file needs a policy

This tool triggers execution of G-code on a CNC router, which controls cutting tools, spindles, and movement of the machine. G-code execution can cause physical damage, waste material, create safety hazards, or destroy workpieces. While not irreversibly destructive in every case (unlike delete_sd_file), execution of malicious or incorrect G-code constitutes a serious threat.

From the tool's definition 'Run a G-code file from the CNC controller' — this tool executes arbitrary G-code programs on physical CNC machinery, which are external operations whose effects depend on the file contents and machine state.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

run_sd_file Rate-limited

run_sd_file 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": {
    "run_sd_file": {
      "limits": [
        {
          "counter": "run_sd_file_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 run_sd_file

What does the run_sd_file tool do? +

Run a G-code file from the CNC controller. 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 run_sd_file? +

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

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

Can I rate-limit run_sd_file? +

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

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

run_sd_file 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.