launch_app · App Screen MCP: Risk & Policy

WHAT IT DOES

What launch_app does on App Screen

AI agents invoke launch_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 launch_app needs a policy

This tool triggers execution of code/processes on a simulated device. While not destructive or financial, it initiates external operations that can have side effects depending on what app is launched and what that app does when started. The impact is high because a misbehaving agent could launch malicious or unintended apps, or launch legitimate apps with uncontrolled consequences.

From the tool's definition Launch an app on a simulator; the tool name is 'launch_app' and executes an external operation (app launch) on an iOS Simulator device whose effects depend on which app is specified as an argument.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

launch_app Rate-limited

launch_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": {
    "launch_app": {
      "limits": [
        {
          "counter": "launch_app_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 App Screen, so you can run agents against it safely.

FAQ

Questions about launch_app

What does the launch_app tool do? +

Launch 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 launch_app? +

Register the App Screen MCP server in PolicyLayer and add a rule for launch_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 launch_app? +

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

Can I rate-limit launch_app? +

Yes. Add a rate_limit block to the launch_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 launch_app completely? +

Set action: deny in the PolicyLayer policy for launch_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 launch_app? +

launch_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.