backup_config · Cnc Fluidnc MCP: Risk & Policy

WHAT IT DOES

What backup_config does on Cnc Fluidnc

AI agents use backup_config 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 backup_config needs a policy

This tool creates a new backup file containing machine settings and work offsets. It is a reversible operation (the backup can be deleted or overwritten later) with no irreversible data loss.

From the tool's definition Tool description states "Save the current FluidNC settings and work offsets to a timestamped backup file." The verb 'Save' indicates creation of new data (the backup file) rather than retrieval or deletion.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

backup_config Rate-limited

backup_config 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": {
    "backup_config": {
      "limits": [
        {
          "counter": "backup_config_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 backup_config

What does the backup_config tool do? +

Save the current FluidNC settings and work offsets to a timestamped backup file. 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 backup_config? +

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

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

Can I rate-limit backup_config? +

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

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

backup_config 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.