ui_execute_with_diff · UI Bridge MCP: Risk & Policy

WHAT IT DOES

What ui_execute_with_diff does on UI Bridge MCP

AI agents invoke ui_execute_with_diff 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_execute_with_diff needs a policy

This tool executes actions on UI elements controlled by the runner, which can trigger side effects ranging from navigation, form submission, clicking buttons, or other interactive operations. While not inherently destructive or financial, it performs active operations that are not merely data retrieval (Read) or simple reversible modifications (Write), placing it in the Execute category.

From the tool's definition Tool name 'ui_execute_with_diff' and description 'Execute an element action in the runner' indicate execution of UI actions.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

ui_execute_with_diff Rate-limited

ui_execute_with_diff 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_execute_with_diff": {
      "limits": [
        {
          "counter": "ui_execute_with_diff_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_execute_with_diff

What does the ui_execute_with_diff tool do? +

Execute an element action 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_execute_with_diff? +

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

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

Can I rate-limit ui_execute_with_diff? +

Yes. Add a rate_limit block to the ui_execute_with_diff 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_execute_with_diff completely? +

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

ui_execute_with_diff 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.