query_selector

Query DOM elements using CSS selector

SERVERBrowser SOURCEmcp-server-browser

Low RISK CLASS

Category Read

Parameters 00 required

Recommended Allowedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/browser/query-selector.md

WHAT IT DOES

What query_selector does on Browser

AI agents call query_selector to retrieve information from Browser without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.

RISK

Why query_selector is rated Low

This tool retrieves DOM element information based on CSS selectors. It reads the browser's current DOM state without modifying, executing code, or triggering external operations. While it operates in a browser context (where other sibling tools like execute_script are Execute category), query_selector itself is a passive read operation analogous to get_* tools on this server.

From the tool's definition Tool description states 'Query DOM elements using CSS selector' - a pure query operation with no modification, execution, or side effects.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs query_selector safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Browser, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For query_selector, this is the rule to start with:

query_selector Allowed

query_selector is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "query_selector": {}
  }
}

ALLOW ONLY THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Browser, apply this rule, and every query_selector call is checked against it from then on.

FAQ

Questions about query_selector

What does the query_selector tool do? +

Query DOM elements using CSS selector. It is categorised as a Read tool in the Browser MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on query_selector? +

Register the Browser MCP server in PolicyLayer and add a rule for 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 Browser. Nothing to install.

What risk level is query_selector? +

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

Can I rate-limit query_selector? +

Yes. Add a rate_limit block to the 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 query_selector completely? +

Set action: deny in the PolicyLayer policy for 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 query_selector? +

query_selector is provided by the Browser MCP server (mcp-server-browser). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

KEEP EXPLORING

More on Browser, and thousands of servers like it.

This server

All 19 Browser tools →

Across the catalogue

claude_query on Claude Bridge → The MCP Attack Database →

Guides

Roll out MCP under one policy →Data exfiltration →MCP token cost →