ui_fill_form · UI Bridge MCP: Risk & Policy

WHAT IT DOES

What ui_fill_form does on UI Bridge MCP

AI agents invoke ui_fill_form 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_fill_form needs a policy

Based on the tool name and server context ('Enables AI to inspect and interact with UI elements'), 'ui_fill_form' likely fills in form fields in a UI, which constitutes an Execute-level action (triggering UI interactions/external operations). Sibling tools like 'sdk_ai_execute' confirm this server supports active UI manipulation.

From the tool's definition Tool name 'ui_fill_form' suggests interacting with UI form elements; description is empty and uninformative.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

ui_fill_form Rate-limited

ui_fill_form 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_fill_form": {
      "limits": [
        {
          "counter": "ui_fill_form_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_fill_form

What does the ui_fill_form tool do? +

ui_fill_form. 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_fill_form? +

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

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

Can I rate-limit ui_fill_form? +

Yes. Add a rate_limit block to the ui_fill_form 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_fill_form completely? +

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

ui_fill_form 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.