vm_stop

Stop a running virtual machine by its ID. Optionally force-stop (power off) instead of graceful shutdown.

SERVERTruenas SOURCEspranab/truenas-mcp

High RISK CLASS

Category Execute

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/spranab-truenas-mcp/vm-stop.md

WHAT IT DOES

What vm_stop does on Truenas

AI agents invoke vm_stop to trigger actions in Truenas. 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.

RISK

Why vm_stop is rated High

This tool triggers an external operation (stopping a VM) whose effects depend on arguments (graceful vs. force shutdown). While not destructive to data, it disrupts service availability and system state. This is Execute rather than Destructive because the VM can be restarted. The 'force-stop' option and potential for service interruption warrant high severity—an agent misusing this could halt critical workloads.

From the tool's definition Tool name 'vm_stop' and description 'Stop a running virtual machine by its ID. Optionally force-stop (power off) instead of graceful shutdown.' indicate execution of control operations on infrastructure.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs vm_stop safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Truenas, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For vm_stop, this is the rule to start with:

vm_stop Rate-limited

vm_stop 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": {
    "vm_stop": {
      "limits": [
        {
          "counter": "vm_stop_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Truenas, apply this rule, and every vm_stop call is checked against it from then on.

FAQ

Questions about vm_stop

What does the vm_stop tool do? +

Stop a running virtual machine by its ID. Optionally force-stop (power off) instead of graceful shutdown. It is categorised as a Execute tool in the Truenas MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on vm_stop? +

Register the Truenas MCP server in PolicyLayer and add a rule for vm_stop: 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 Truenas. Nothing to install.

What risk level is vm_stop? +

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

Can I rate-limit vm_stop? +

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

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

vm_stop is provided by the Truenas MCP server (spranab/truenas-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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