update_vm · Truenas Ws MCP: Risk & Policy

WHAT IT DOES

What update_vm does on Truenas Ws

AI agents use update_vm to create or update resources in Truenas Ws — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Truenas Ws environment.

WHY IT NEEDS A POLICY

Why update_vm needs a policy

This tool modifies VM configuration parameters (RAM, CPUs) but does not delete VMs or irreversibly destroy data. Changes to VM resources are reversible — an admin can adjust RAM or CPU counts again. This is a Write operation rather than Destructive.

From the tool's definition Tool description states 'Update VM configuration (RAM, CPUs, etc.)' — this modifies VM settings reversibly. The sibling tools (create_dataset, create_snapshot, create_user) confirm this server performs state-changing operations.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_vm Rate-limited

update_vm 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": {
    "update_vm": {
      "limits": [
        {
          "counter": "update_vm_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 Truenas Ws, so you can run agents against it safely.

FAQ

Questions about update_vm

What does the update_vm tool do? +

Update VM configuration (RAM, CPUs, etc.). It is categorised as a Write tool in the Truenas Ws MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on update_vm? +

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

What risk level is update_vm? +

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

Can I rate-limit update_vm? +

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

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

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