create_snapshot · Truenas Ws MCP: Risk & Policy

WHAT IT DOES

What create_snapshot does on Truenas Ws

AI agents use create_snapshot 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 create_snapshot needs a policy

This tool performs a write operation by creating a new snapshot object in the ZFS filesystem. Snapshots are reversible—they can be deleted without affecting the original dataset—distinguishing this from destructive operations.

From the tool's definition Tool creates a manual ZFS snapshot, a reversible state capture that modifies the snapshot metadata and storage allocation without destroying data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_snapshot Rate-limited

create_snapshot 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": {
    "create_snapshot": {
      "limits": [
        {
          "counter": "create_snapshot_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 create_snapshot

What does the create_snapshot tool do? +

Create a manual ZFS snapshot. 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 create_snapshot? +

Register the Truenas Ws MCP server in PolicyLayer and add a rule for create_snapshot: 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 create_snapshot? +

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

Can I rate-limit create_snapshot? +

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

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

create_snapshot 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.