water_heater_control · Homeassistant MCP: Risk & Policy

WHAT IT DOES

What water_heater_control does on Homeassistant

AI agents invoke water_heater_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 water_heater_control needs a policy

The tool name implies controlling a physical water heater device. Based on the server's purpose ('control Home Assistant devices and services') and sibling tools like climate_control, cover_control, alarm_control — all of which trigger real-world physical actions — this tool likely executes commands to change water heater state (temperature setpoint, on/off, mode).

From the tool's definition Tool name 'water_heater_control' on a Home Assistant MCP server designed to 'control Home Assistant devices and services'

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

water_heater_control Rate-limited

water_heater_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": {
    "water_heater_control": {
      "limits": [
        {
          "counter": "water_heater_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 water_heater_control

What does the water_heater_control tool do? +

water_heater_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 water_heater_control? +

Register the Homeassistant MCP server in PolicyLayer and add a rule for water_heater_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 water_heater_control? +

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

Can I rate-limit water_heater_control? +

Yes. Add a rate_limit block to the water_heater_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 water_heater_control completely? +

Set action: deny in the PolicyLayer policy for water_heater_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 water_heater_control? +

water_heater_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.