ui_focus · UI Bridge MCP: Risk & Policy

WHAT IT DOES

What ui_focus does on UI Bridge MCP

AI agents invoke ui_focus to trigger actions in UI Bridge 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 ui_focus needs a policy

Focusing a UI element triggers an external UI interaction/operation on a running application. This is not a passive read—it actively changes the UI state (focus state of an element), constituting an execution of a UI action. While not destructive or financial, it performs an operation with side effects on an external UI, placing it in the Execute category.

From the tool's definition Focus an element in the runner

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

ui_focus Rate-limited

ui_focus 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": {
    "ui_focus": {
      "limits": [
        {
          "counter": "ui_focus_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 UI Bridge MCP, so you can run agents against it safely.

FAQ

Questions about ui_focus

What does the ui_focus tool do? +

Focus an element in the runner. It is categorised as a Execute tool in the UI Bridge 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 ui_focus? +

Register the UI Bridge MCP server in PolicyLayer and add a rule for ui_focus: 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 UI Bridge MCP. Nothing to install.

What risk level is ui_focus? +

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

Can I rate-limit ui_focus? +

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

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

ui_focus is provided by the UI Bridge MCP server (qontinui/ui-bridge-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.