subnet_scan · Keel MCP: Risk & Policy

WHAT IT DOES

What subnet_scan does on Keel

AI agents invoke subnet_scan to trigger actions in Keel. 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 subnet_scan needs a policy

This tool actively probes network hosts by scanning ports across a subnet, which constitutes an external operation with potential side effects. Port scanning can trigger security alerts, affect target systems, and reveal network topology. It goes beyond passive reading — it sends packets to multiple hosts and ports, making it an Execute-category tool.

From the tool's definition Discover live hosts on a local subnet by probing common ports

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

subnet_scan Rate-limited

subnet_scan 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": {
    "subnet_scan": {
      "limits": [
        {
          "counter": "subnet_scan_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 Keel, so you can run agents against it safely.

FAQ

Questions about subnet_scan

What does the subnet_scan tool do? +

Discover live hosts on a local subnet by probing common ports. It is categorised as a Execute tool in the Keel MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on subnet_scan? +

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

What risk level is subnet_scan? +

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

Can I rate-limit subnet_scan? +

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

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

subnet_scan is provided by the Keel MCP server (seayniclabs/keel). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.