focus_window · Mac MCP: Risk & Policy

WHAT IT DOES

What focus_window does on Mac

AI agents invoke focus_window to trigger actions in Mac. 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 focus_window needs a policy

This tool triggers an external OS operation (window focus/raise) that affects the state of the macOS windowing system. It's not merely reading data, nor does it create/modify data in the traditional sense — it executes a system-level action (via AppleScript/JXA) that changes UI state.

From the tool's definition Brings a specific window to the front by app name and optional window index

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

focus_window Rate-limited

focus_window 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": {
    "focus_window": {
      "limits": [
        {
          "counter": "focus_window_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 Mac, so you can run agents against it safely.

FAQ

Questions about focus_window

What does the focus_window tool do? +

Brings a specific window to the front by app name and optional window index. It is categorised as a Execute tool in the Mac MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on focus_window? +

Register the Mac MCP server in PolicyLayer and add a rule for focus_window: 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 Mac. Nothing to install.

What risk level is focus_window? +

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

Can I rate-limit focus_window? +

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

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

focus_window is provided by the Mac MCP server (laststance/mac-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.