sys_cron · RedisNexus MCP: Risk & Policy

WHAT IT DOES

What sys_cron does on RedisNexus

AI agents invoke sys_cron to trigger actions in RedisNexus. 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 sys_cron needs a policy

This tool can add and remove scheduled cron jobs, which triggers external operations on a schedule. Adding or removing cron jobs can have significant system-wide effects — malicious or erroneous cron jobs could execute arbitrary commands repeatedly.

From the tool's definition Manage cron jobs: list, add, remove, and AI-generate cron expressions

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

sys_cron Rate-limited

sys_cron 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": {
    "sys_cron": {
      "limits": [
        {
          "counter": "sys_cron_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 RedisNexus, so you can run agents against it safely.

FAQ

Questions about sys_cron

What does the sys_cron tool do? +

Manage cron jobs: list, add, remove, and AI-generate cron expressions. It is categorised as a Execute tool in the RedisNexus MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on sys_cron? +

Register the RedisNexus MCP server in PolicyLayer and add a rule for sys_cron: 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 RedisNexus. Nothing to install.

What risk level is sys_cron? +

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

Can I rate-limit sys_cron? +

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

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

sys_cron is provided by the RedisNexus MCP server (rajkumar-madhu/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

// THE FULL RECORD

sys_cron is one line of RedisNexus's registry record.

The record carries the whole server: verified identity, auth posture, risk grade, every tool classified, recommended policy — re-checked continuously.

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