shutoff_valve · Home Controller MCP: Risk & Policy

WHAT IT DOES

What shutoff_valve does on Home Controller

AI agents invoke shutoff_valve to trigger actions in Home Controller. 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 shutoff_valve needs a policy

This tool directly actuates a physical water shutoff valve in the real world. Closing the valve cuts off water supply to the entire property (high blast radius), and opening it could flood a property if done at the wrong time.

From the tool's definition 'Open or close the water shutoff valve' — triggers a physical actuation of a real-world valve that controls water flow to the premises

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

shutoff_valve Rate-limited

shutoff_valve 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": {
    "shutoff_valve": {
      "limits": [
        {
          "counter": "shutoff_valve_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 Home Controller, so you can run agents against it safely.

FAQ

Questions about shutoff_valve

What does the shutoff_valve tool do? +

Open or close the water shutoff valve (Phyn Plus only). It is categorised as a Execute tool in the Home Controller MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on shutoff_valve? +

Register the Home Controller MCP server in PolicyLayer and add a rule for shutoff_valve: 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 Home Controller. Nothing to install.

What risk level is shutoff_valve? +

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

Can I rate-limit shutoff_valve? +

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

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

shutoff_valve is provided by the Home Controller MCP server (winsthuang/home-controller). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.