AI agents invoke cronjob_create 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.
Creating a cron job schedules recurring execution of commands or scripts on the system. This enables arbitrary code execution on a schedule, making it an Execute-category action with high severity since a misused cron job could repeatedly run malicious or destructive commands.
From the tool's definition Create a new cron job
Documented attack patterns abuse exactly the kind of access cronjob_create 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_create:
{
"version": "1",
"default": "deny",
"tools": {
"cronjob_create": {
"limits": [
{
"counter": "cronjob_create_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}cronjob_create 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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Create a new cron job. 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_create: 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_create 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_create 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_create. 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_create 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.