execute_javascript

Execute JavaScript code in the browser context. Args: code: JavaScript code to execute Returns: Result of the JavaScript execution

SERVERChrome Devtools SOURCEbenjaminr/chrome-devtools-mcp

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/benjaminr-chrome-devtools-mcp/execute-javascript.md

WHAT IT DOES

What execute_javascript does on Chrome Devtools

AI agents invoke execute_javascript to trigger actions in Chrome Devtools. 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 execute_javascript is rated High

This tool directly executes arbitrary code (JavaScript) in a live browser environment, which is the definition of the Execute category. The blast radius is high because an AI agent could use this to steal credentials, modify page content, exfiltrate data, perform phishing attacks, or interact with web applications in harmful ways.

From the tool's definition Tool name is 'execute_javascript' and description states it 'Execute[s] JavaScript code in the browser context.' The argument 'code' accepts arbitrary JavaScript to be executed.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs execute_javascript safely

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

execute_javascript Rate-limited

execute_javascript 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": {
    "execute_javascript": {
      "limits": [
        {
          "counter": "execute_javascript_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, apply this rule, and every execute_javascript call is checked against it from then on.

FAQ

Questions about execute_javascript

What does the execute_javascript tool do? +

Execute JavaScript code in the browser context. Args: code: JavaScript code to execute Returns: Result of the JavaScript execution. It is categorised as a Execute tool in the Chrome Devtools MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on execute_javascript? +

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

What risk level is execute_javascript? +

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

Can I rate-limit execute_javascript? +

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

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

execute_javascript is provided by the Chrome Devtools MCP server (benjaminr/chrome-devtools-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

KEEP EXPLORING

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