valve_control · Homeassistant MCP: Risk & Policy

WHAT IT DOES

What valve_control does on Homeassistant

AI agents invoke valve_control to trigger actions in Homeassistant. 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 valve_control needs a policy

Based on the tool name and server context, valve_control likely triggers physical valve actuators (e.g., water, gas shutoff valves) in a smart home environment. Controlling physical infrastructure like water or gas valves is an Execute-level action with high blast radius — misuse could cause flooding, gas leaks, or property damage.

From the tool's definition Tool name 'valve_control' on a Home Assistant MCP server that controls devices and services; description is empty and uninformative.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

valve_control Rate-limited

valve_control 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": {
    "valve_control": {
      "limits": [
        {
          "counter": "valve_control_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 Homeassistant, so you can run agents against it safely.

FAQ

Questions about valve_control

What does the valve_control tool do? +

valve_control. It is categorised as a Execute tool in the Homeassistant MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on valve_control? +

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

What risk level is valve_control? +

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

Can I rate-limit valve_control? +

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

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

valve_control is provided by the Homeassistant MCP server (robbrad/homeassistant-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.