evaluate

Evaluates a JavaScript script

SERVERChrome Devtools SOURCE@async23/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/async23-chrome-devtools-mcp/evaluate.md

WHAT IT DOES

What evaluate does on Chrome Devtools

AI agents invoke evaluate 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 evaluate is rated High

Executing arbitrary JavaScript in a live browser session can access cookies, credentials, DOM, local storage, make network requests, exfiltrate data, or manipulate page state. This is the highest-risk Execute action with critical blast radius if misused by an AI agent.

From the tool's definition 'Evaluates a JavaScript script' — executes arbitrary JavaScript in a live browser context

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs evaluate 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 evaluate, this is the rule to start with:

evaluate Rate-limited

evaluate 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": {
      "limits": [
        {
          "counter": "evaluate_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 evaluate call is checked against it from then on.

FAQ

Questions about evaluate

What does the evaluate tool do? +

Evaluates a JavaScript script. 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 evaluate? +

Register the Chrome Devtools MCP server in PolicyLayer and add a rule for evaluate: 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 evaluate? +

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

Can I rate-limit evaluate? +

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

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

evaluate is provided by the Chrome Devtools MCP server (@async23/chrome-devtools-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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