type_text · App Screen MCP: Risk & Policy

WHAT IT DOES

What type_text does on App Screen

AI agents invoke type_text 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 type_text needs a policy

This tool triggers an external operation (text input) on an iOS Simulator's focused UI element. It can cause side effects depending on context — submitting forms, entering credentials, triggering searches, or sending messages — making it an Execute-category action. Misuse could lead to unintended data entry or actions within apps, warranting medium severity.

From the tool's definition Type text into the currently focused element on the simulator

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

type_text Rate-limited

type_text 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": {
    "type_text": {
      "limits": [
        {
          "counter": "type_text_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 type_text

What does the type_text tool do? +

Type text into the currently focused element on the 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 type_text? +

Register the App Screen MCP server in PolicyLayer and add a rule for type_text: 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 type_text? +

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

Can I rate-limit type_text? +

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

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

type_text 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.