ui_blur · UI Bridge MCP: Risk & Policy

WHAT IT DOES

What ui_blur does on UI Bridge MCP

AI agents invoke ui_blur 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_blur needs a policy

Removing focus from a UI element is an external UI operation that produces a side effect (changing focus state) in the runner application. It's not purely reading data, nor does it write/delete persistent data. It falls under Execute as it triggers a UI action whose effect depends on the target element. Blast radius is low since defocusing an element is a minor, generally reversible UI state change.

From the tool's definition 'Remove focus from an element in the runner' — triggers a UI interaction (blur/defocus) on an element

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

ui_blur Rate-limited

ui_blur 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_blur": {
      "limits": [
        {
          "counter": "ui_blur_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_blur

What does the ui_blur tool do? +

Remove focus from 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_blur? +

Register the UI Bridge MCP server in PolicyLayer and add a rule for ui_blur: 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_blur? +

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

Can I rate-limit ui_blur? +

Yes. Add a rate_limit block to the ui_blur 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_blur completely? +

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

ui_blur 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.