Attempt to focus a window by application name.
AI agents invoke focus_window to trigger actions in Kwin. 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.
Focusing a window triggers an external desktop operation — it manipulates the window manager state (raising and activating a window) rather than simply reading data or writing a file. It has side effects on the live desktop session, potentially exposing or bringing to the foreground sensitive windows.
From the tool's definition Attempt to focus a window by application name
Documented attack patterns abuse exactly the kind of access focus_window gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Kwin, and nothing reaches the server without passing your rules. This is the rule we recommend for focus_window:
{
"version": "1",
"default": "deny",
"tools": {
"focus_window": {
"limits": [
{
"counter": "focus_window_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}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.
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Attempt to focus a window by application name. It is categorised as a Execute tool in the Kwin MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Kwin 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 Kwin. Nothing to install.
focus_window is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
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.
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.
focus_window is provided by the Kwin MCP server (isac322/kwin-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Kwin, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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30 Kwin tools catalogued and risk-classified — across an index of 43,000+ MCP servers.