create_cron_job · Nexus Core MCP: Risk & Policy

WHAT IT DOES

What create_cron_job does on Nexus Core

AI agents invoke create_cron_job to trigger actions in Nexus Core. 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 IT NEEDS A POLICY

Why create_cron_job needs a policy

Cron jobs execute actions repeatedly on a schedule. An AI agent could misuse this to schedule destructive, financial, or other high-impact operations to run indefinitely without user intervention. The blast radius is high because the effects are recurring and potentially unbounded.

From the tool's definition 'Register a recurring action' with 'standard 5-field cron string' — schedules repeated execution of arbitrary actions on a time-based trigger

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_cron_job Rate-limited

create_cron_job 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.

View as policy code

policy.json

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

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Nexus Core, so you can run agents against it safely.

FAQ

Questions about create_cron_job

What does the create_cron_job tool do? +

Register a recurring action. schedule_expression is a standard 5-field cron string. It is categorised as a Execute tool in the Nexus Core MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on create_cron_job? +

Register the Nexus Core MCP server in PolicyLayer and add a rule for create_cron_job: 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 Nexus Core. Nothing to install.

What risk level is create_cron_job? +

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

Can I rate-limit create_cron_job? +

Yes. Add a rate_limit block to the create_cron_job 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 create_cron_job completely? +

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

create_cron_job is provided by the Nexus Core MCP server (noumenon-ai/nexus-core). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.