app_open · Goose App Maker MCP: Risk & Policy

WHAT IT DOES

What app_open does on Goose App Maker MCP

AI agents invoke app_open to trigger actions in Goose App Maker MCP. 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 app_open needs a policy

This tool executes an external operation by opening a web browser and potentially starting a web server if the app isn't already being served. It triggers side effects beyond simple data retrieval, making it Execute rather than Read.

From the tool's definition 'Open an app in the default web browser' and 'If the app is not currently being served' implies triggering external operations (launching browser, potentially starting a server)

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

app_open Rate-limited

app_open 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": {
    "app_open": {
      "limits": [
        {
          "counter": "app_open_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 Goose App Maker MCP, so you can run agents against it safely.

FAQ

Questions about app_open

What does the app_open tool do? +

Open an app in the default web browser. If the app is not currently being served,. It is categorised as a Execute tool in the Goose App Maker 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 app_open? +

Register the Goose App Maker MCP server in PolicyLayer and add a rule for app_open: 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 Goose App Maker MCP. Nothing to install.

What risk level is app_open? +

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

Can I rate-limit app_open? +

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

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

app_open is provided by the Goose App Maker MCP server (michaelneale/goose-app-maker-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.