update_check

THE RISK

Low Risk

Why update_check needs a policy

This tool only retrieves and returns information about available updates without applying any changes. It is a read-only query operation with no side effects.

From the tool's definition Check for available system updates. Returns information about pending updates and the current train.

Documented attack patterns abuse exactly the kind of access update_check gives an agent:

POLICY

How to control update_check

PolicyLayer is an MCP gateway — it sits between your AI agents and Truenas, and nothing reaches the server without passing your rules. This is the rule we recommend for update_check:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "update_check": {}
  }
}

update_check is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register Truenas — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

CAP THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about update_check

What does the update_check tool do? +

Check for available system updates. Returns information about pending updates and the current train. It is categorised as a Read tool in the Truenas MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on update_check? +

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

update_check is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit update_check? +

Yes. Add a rate_limit block to the update_check 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_check completely? +

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

update_check 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.

Enforce policy on every Truenas tool call.

Start from Truenas, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →