AI agents invoke cronjob_run 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.
This tool executes code/commands by running a cron job outside its normal schedule. While the actual impact depends on what the cron job contains, the tool itself enables arbitrary command execution on the TrueNAS system. This is Execute rather than Destructive because the harm is contingent on the cron job's contents, not inherent to the tool.
From the tool's definition Tool name 'cronjob_run' combined with description 'Run a cron job immediately' indicates execution of scheduled tasks. The action 'Run' triggers external operations whose effects depend on the cron job's configured commands and arguments.
Documented attack patterns abuse exactly the kind of access cronjob_run gives an agent:
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 cronjob_run:
{
"version": "1",
"default": "deny",
"tools": {
"cronjob_run": {
"limits": [
{
"counter": "cronjob_run_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}cronjob_run 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.
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Run a cron job immediately. 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 cronjob_run: 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.
cronjob_run 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 cronjob_run 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 cronjob_run. 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.
cronjob_run 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.
Start from Truenas, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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279 Truenas tools catalogued and risk-classified — across an index of 43,000+ MCP servers.