fan_control · Homeassistant MCP: Risk & Policy

WHAT IT DOES

What fan_control does on Homeassistant

AI agents invoke fan_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 fan_control needs a policy

The tool name implies controlling a fan device in Home Assistant. Based on the server description about controlling devices, this likely triggers physical device state changes (on/off, speed, direction), making it an Execute-level action. However, the description is empty, lowering confidence. Severity is medium as misuse could affect physical environment (e.g., running fans unexpectedly) but is generally reversible.

From the tool's definition Tool name 'fan_control' on a Home Assistant MCP server that 'Enables AI assistants to control Home Assistant devices and services'

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

fan_control Rate-limited

fan_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": {
    "fan_control": {
      "limits": [
        {
          "counter": "fan_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 fan_control

What does the fan_control tool do? +

fan_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 fan_control? +

Register the Homeassistant MCP server in PolicyLayer and add a rule for fan_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 fan_control? +

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

Can I rate-limit fan_control? +

Yes. Add a rate_limit block to the fan_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 fan_control completely? +

Set action: deny in the PolicyLayer policy for fan_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 fan_control? +

fan_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.