update_download

THE RISK

High Risk

Why update_download needs a policy

Downloading system updates triggers an external operation (fetching update packages from remote servers) with side effects such as network usage and disk writes. It is not purely reading data, and it modifies the local system state by storing update files. Since the actual update is deferred to update_apply, it is not yet Destructive, making Execute the most appropriate category.

From the tool's definition Download pending system updates. This starts the download process

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

POLICY

How to control update_download

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_download:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "update_download": {
      "limits": [
        {
          "counter": "update_download_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

update_download 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.

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.

RATE-LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Truenas tools

Destructive acme_dns_authenticator_delete Delete an ACME DNS authenticator by its ID. Destructive alertservice_delete Delete an alert notification service by its ID. Use alertservice_list to find the ID. Destructive api_key_delete Delete an API key by its numeric ID. Use api_key_list to find the ID. This immediately rev Destructive app_delete Delete/uninstall an app. This is a DESTRUCTIVE operation. The Destructive bootenv_delete Delete a boot environment. This is a DESTRUCTIVE operation — the Destructive certificate_delete Delete a certificate by its ID. This is a DESTRUCTIVE operation — the Destructive cloud_backup_delete Delete a cloud backup task (destructive — requires confirm) Destructive cloudsync_credentials_delete Delete a cloud sync credential

All 279 Truenas tools →

Execute tools on other servers

Android Forensics ADB MCP Server adb_shell_command EMBA-MCP run_emba_scan Frida Game Hacking MCP remove_breakpoint Procmon request_elevation

Go deeper

High-risk tools in Truenas → Every high-risk tool this server exposes, in one view.
All high-risk MCP tools → Every high-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about update_download

What does the update_download tool do? +

Download pending system updates. This starts the download process; the system is not updated until update_apply is called. 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 update_download? +

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

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

Can I rate-limit update_download? +

Yes. Add a rate_limit block to the update_download 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_download completely? +

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

update_download 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 →