ui_scroll · UI Bridge MCP: Risk & Policy

WHAT IT DOES

What ui_scroll does on UI Bridge MCP

AI agents invoke ui_scroll 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_scroll needs a policy

Scrolling is a UI interaction that causes an external application to change its visual state. It goes beyond reading data (no retrieval) and beyond writing data (no persistent modification), but it does trigger an external operation on a live UI element, placing it in the Execute category. Misuse could cause unintended navigation or UI state changes, warranting medium severity.

From the tool's definition "Scroll within an element in the runner" — triggers a UI interaction (scroll action) within a running application

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

ui_scroll Rate-limited

ui_scroll 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_scroll": {
      "limits": [
        {
          "counter": "ui_scroll_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_scroll

What does the ui_scroll tool do? +

Scroll within 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_scroll? +

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

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

Can I rate-limit ui_scroll? +

Yes. Add a rate_limit block to the ui_scroll 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_scroll completely? +

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

ui_scroll 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.