terminate_app · App Screen MCP: Risk & Policy

WHAT IT DOES

What terminate_app does on App Screen

AI agents invoke terminate_app to trigger actions in App Screen. 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 terminate_app needs a policy

Force-quitting an app is an external operation that triggers a process termination on the iOS Simulator. It is not purely destructive (no data is permanently deleted), but it executes an action with real side effects (killing a running process), making Execute the most appropriate category. Misuse could interrupt running workflows or cause data loss in unsaved app state, warranting medium severity.

From the tool's definition Terminate (force-quit) an app on a simulator

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

terminate_app Rate-limited

terminate_app 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": {
    "terminate_app": {
      "limits": [
        {
          "counter": "terminate_app_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

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Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches App Screen, so you can run agents against it safely.

FAQ

Questions about terminate_app

What does the terminate_app tool do? +

Terminate (force-quit) an app on a simulator. It is categorised as a Execute tool in the App Screen MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on terminate_app? +

Register the App Screen MCP server in PolicyLayer and add a rule for terminate_app: 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 App Screen. Nothing to install.

What risk level is terminate_app? +

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

Can I rate-limit terminate_app? +

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

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

terminate_app is provided by the App Screen MCP server (xmuweili/app-screen-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.