web_performance · Fourth Playwright MCP Server MCP

WHAT IT DOES

What web_performance does on Fourth Playwright MCP Server

AI agents invoke web_performance to trigger actions in Fourth Playwright MCP 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 web_performance needs a policy

Performance tools typically trigger code execution within the browser (e.g., measuring timing, DOM analysis, network inspection, JavaScript execution). Given the sibling tools' focus on browser automation and execution, this tool likely executes operations whose side effects depend on the browser state and any injected code.

From the tool's definition Tool name 'web_performance' combined with sibling tools like 'web_execute_js', 'playwright_navigate', and 'browser_wait_for' indicates this is part of a Playwright browser automation suite.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

web_performance Rate-limited

web_performance 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": {
    "web_performance": {
      "limits": [
        {
          "counter": "web_performance_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 Fourth Playwright MCP Server, so you can run agents against it safely.

FAQ

Questions about web_performance

What does the web_performance tool do? +

web_performance. It is categorised as a Execute tool in the Fourth Playwright MCP 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 web_performance? +

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

What risk level is web_performance? +

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

Can I rate-limit web_performance? +

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

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

web_performance is provided by the Fourth Playwright MCP Server MCP server (rev4nchist/fourth-playwright-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.