ui_query_selector · UI Bridge MCP: Risk & Policy

WHAT IT DOES

What ui_query_selector does on UI Bridge MCP

AI agents call ui_query_selector to retrieve information from UI Bridge MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.

WHY IT NEEDS A POLICY

Why ui_query_selector needs a policy

Query/selector tools retrieve UI element information to support inspection workflows. While the description is empty (reducing confidence slightly), the name and server context strongly suggest this is a read-only inspection capability. Even in control/SDK modes, querying UI elements does not alter state, execute code, or create side effects unless paired with separate action tools.

From the tool's definition Tool name 'ui_query_selector' indicates a DOM/UI querying function that retrieves element metadata without modification.

Attacks that exploit this kind of access

Questions about ui_query_selector

What does the ui_query_selector tool do? +

ui_query_selector. It is categorised as a Read tool in the UI Bridge MCP MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on ui_query_selector? +

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

ui_query_selector is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit ui_query_selector? +

Yes. Add a rate_limit block to the ui_query_selector 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_query_selector completely? +

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

ui_query_selector 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.