evaluate_script

Evaluate a JavaScript function inside the currently selected page. Returns the response as JSON so returned values have to JSON-serializable.

SERVERChrome DevTools MCP SOURCEanirbandz/chrome_mcp_devtool

High RISK CLASS

Category Execute

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/anirbandz-chrome-mcp-devtool/evaluate-script.md

WHAT IT DOES

What evaluate_script does on Chrome DevTools MCP

AI agents invoke evaluate_script to trigger actions in Chrome DevTools MCP. 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.

RISK

Why evaluate_script is rated High

This tool executes arbitrary JavaScript in a live browser page. An AI agent could use it to run any code — exfiltrate data, manipulate the DOM, make network requests, trigger destructive actions, or interact with any web application state. Arbitrary code execution in a browser context is critical severity.

From the tool's definition "Evaluate a JavaScript function inside the currently selected page"

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs evaluate_script safely

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

evaluate_script Rate-limited

evaluate_script 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": {
    "evaluate_script": {
      "limits": [
        {
          "counter": "evaluate_script_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL → Instant setup, no code required.

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

FAQ

Questions about evaluate_script

What does the evaluate_script tool do? +

Evaluate a JavaScript function inside the currently selected page. Returns the response as JSON so returned values have to JSON-serializable. It is categorised as a Execute tool in the Chrome DevTools MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on evaluate_script? +

Register the Chrome DevTools MCP server in PolicyLayer and add a rule for evaluate_script: 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 Chrome DevTools MCP. Nothing to install.

What risk level is evaluate_script? +

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

Can I rate-limit evaluate_script? +

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

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

evaluate_script is provided by the Chrome DevTools MCP server (anirbandz/chrome_mcp_devtool). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

KEEP EXPLORING

More on Chrome DevTools, and thousands of servers like it.

This server

All 26 Chrome DevTools tools → High-risk tools on this server →

Across the catalogue

load_script on Frida Game Hacking MCP → All high-risk MCP tools → The MCP Attack Database →

Guides

Govern code and CI agents →Agent sandbox →Least privilege for MCP →