fan_control

THE RISK

High Risk

Why fan_control needs a policy

This tool triggers physical device state changes (turning fans on/off, adjusting speed/modes/oscillation) in the real world via HomeAssistant. It is not merely reading data, nor is it destructive or financial. It executes external operations whose effects depend on arguments, fitting the Execute category. Misuse could cause discomfort or energy waste but has limited blast radius.

From the tool's definition Control fans. Turn on/off, set speed percentage, preset modes, oscillation.

Documented attack patterns abuse exactly the kind of access fan_control gives an agent:

POLICY

How to control fan_control

PolicyLayer is an MCP gateway — it sits between your AI agents and HomeAssistant MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for fan_control:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "fan_control": {
      "limits": [
        {
          "counter": "fan_control_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

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.

Create a free account and register HomeAssistant MCP — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

RATE-LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More HomeAssistant MCP tools

Execute alarm_control Control alarm systems. Arm (home, away, night), disarm, or trigger alarms. Execute automation Manage Home Assistant automations. List all automations, toggle on/off, or trigger manuall Execute vacuum_control Control robot vacuums. Start, pause, stop, return to dock, clean spot, locate. Execute climate_control Control climate devices (thermostats, AC) in Home Assistant. List devices, get state, set Execute cover_control Control covers (blinds, curtains, garage doors). Open, close, stop, or set position. Execute lock_control Control locks. Lock, unlock, or open (for locks that support unlatching). Execute media_player_control Control media players. Play, pause, stop, volume control, and source selection. Execute scene Manage and activate Home Assistant scenes.

All 13 HomeAssistant MCP tools →

Execute tools on other servers

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Go deeper

High-risk tools in HomeAssistant MCP → Every high-risk tool this server exposes, in one view.
All high-risk MCP tools → Every high-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about fan_control

What does the fan_control tool do? +

Control fans. Turn on/off, set speed percentage, preset modes, oscillation. It is categorised as a Execute tool in the HomeAssistant MCP 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 MCP. 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 (jango-blockchained/advanced-homeassistant-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every HomeAssistant MCP tool call.

Start from HomeAssistant MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →