wait_for_selector · MCP Playwright Server MCP: Risk & Policy

WHAT IT DOES

What wait_for_selector does on MCP Playwright Server

AI agents invoke wait_for_selector to trigger actions in MCP Playwright Server. 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 wait_for_selector needs a policy

This tool controls browser behavior by waiting for a specific DOM state, making it an execution/automation action rather than a pure read. It has minimal blast radius as it only affects timing/flow of browser automation, not data or systems, hence low severity.

From the tool's definition 'Wait for an element matching the selector to appear or reach a specific state' — triggers a browser automation action that pauses execution until a DOM condition is met

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

wait_for_selector Rate-limited

wait_for_selector 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": {
    "wait_for_selector": {
      "limits": [
        {
          "counter": "wait_for_selector_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 MCP Playwright Server, so you can run agents against it safely.

FAQ

Questions about wait_for_selector

What does the wait_for_selector tool do? +

Wait for an element matching the selector to appear or reach a specific state. It is categorised as a Execute tool in the MCP Playwright Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on wait_for_selector? +

Register the MCP Playwright Server MCP server in PolicyLayer and add a rule for wait_for_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 MCP Playwright Server. Nothing to install.

What risk level is wait_for_selector? +

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

Can I rate-limit wait_for_selector? +

Yes. Add a rate_limit block to the wait_for_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 wait_for_selector completely? +

Set action: deny in the PolicyLayer policy for wait_for_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 wait_for_selector? +

wait_for_selector is provided by the MCP Playwright Server MCP server (j0hanz/playwright-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.