update_download
Download pending system updates. This starts the download process; the system is not updated until update_apply is called.
This record as markdown: /tools/spranab-truenas-mcp/update-download.md
What update_download does on Truenas
AI agents invoke update_download 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.
Why update_download is rated High
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
Attacks that exploit this kind of access
The rule that runs update_download 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 update_download, this is the rule to start with:
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.
The button opens the PolicyLayer dashboard: create your workspace, connect Truenas, apply this rule, and every update_download call is checked against it from then on.
Questions about update_download
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.
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.
update_download is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
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.
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.
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.
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