web_execute_js · Fourth Playwright MCP Server MCP

WHAT IT DOES

What web_execute_js does on Fourth Playwright MCP Server

AI agents invoke web_execute_js 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_execute_js needs a policy

JavaScript execution in a browser is a classic Execute category risk. The tool can interact with the DOM, trigger API calls, modify page state, or perform actions based on arbitrary code passed by the caller. Without guardrails or sandboxing visible in the empty description, misuse could lead to unauthorized transactions, credential theft, or manipulation of the Fourth platform.

From the tool's definition Tool name 'web_execute_js' indicates execution of arbitrary JavaScript in a browser context. Combined with server description stating Playwright browser automation integration, this tool runs code with side effects dependent on arguments.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

web_execute_js Rate-limited

web_execute_js 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_execute_js": {
      "limits": [
        {
          "counter": "web_execute_js_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_execute_js

What does the web_execute_js tool do? +

web_execute_js. 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_execute_js? +

Register the Fourth Playwright MCP Server MCP server in PolicyLayer and add a rule for web_execute_js: 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_execute_js? +

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

Can I rate-limit web_execute_js? +

Yes. Add a rate_limit block to the web_execute_js 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_execute_js completely? +

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

web_execute_js 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.