stop_scene · HC3 MCP Server MCP: Risk & Policy

WHAT IT DOES

What stop_scene does on HC3 MCP Server

AI agents invoke stop_scene to trigger actions in HC3 MCP Server. 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 stop_scene needs a policy

This tool executes a command against the smart home system that halts an ongoing automation/scene. While not destructive (the scene can be restarted) and not creating permanent data loss, it is an Execute-category tool because it actively triggers an external operation whose effects (stopping specific scenes) depend on the provided arguments.

From the tool's definition Tool performs an action that 'stops a running scene' - this is an external operation with effects that depend on arguments (the scene ID). The tool triggers an active process termination in the Fibaro Home Center 3 system.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

stop_scene Rate-limited

stop_scene 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": {
    "stop_scene": {
      "limits": [
        {
          "counter": "stop_scene_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 HC3 MCP Server, so you can run agents against it safely.

FAQ

Questions about stop_scene

What does the stop_scene tool do? +

Stop a running scene by ID. It is categorised as a Execute tool in the HC3 MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on stop_scene? +

Register the HC3 MCP Server MCP server in PolicyLayer and add a rule for stop_scene: 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 HC3 MCP Server. Nothing to install.

What risk level is stop_scene? +

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

Can I rate-limit stop_scene? +

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

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

stop_scene is provided by the HC3 MCP Server MCP server (jangabrielsson/hc3_mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.