list_extensions

THE RISK

Low Risk

Why list_extensions needs a policy

This tool retrieves and queries information about browser extensions without modifying, deleting, or executing anything. It presents no direct harm even if misused by an AI agent, though the information could inform subsequent attacks. Classified as Read with low severity due to minimal blast radius.

From the tool's definition Tool 'list_extensions' lists installed Chrome extensions with metadata (name, ID, version, enabled status). The verb 'list' and scope limited to retrieval with no modification, deletion, or execution confirms read-only behavior.

Documented attack patterns abuse exactly the kind of access list_extensions gives an agent:

POLICY

How to control list_extensions

PolicyLayer is an MCP gateway — it sits between your AI agents and Chrome DevTools, and nothing reaches the server without passing your rules. This is the rule we recommend for list_extensions:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "list_extensions": {}
  }
}

list_extensions is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register Chrome DevTools — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

CAP THIS TOOL →

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EXPLORE

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Go deeper

Roll out MCP under one policy → Per-person scoped tokens, one central policy, and full audit across every server your team connects.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →
PolicyLayer vs alternatives → How deterministic, per-call MCP policy compares with gateways, identity layers, and authorisation platforms.

FAQ

Questions about list_extensions

What does the list_extensions tool do? +

Lists all the Chrome extensions installed in the browser. This includes their name, ID, version, and enabled status. It is categorised as a Read tool in the Chrome DevTools MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on list_extensions? +

Register the Chrome DevTools MCP server in PolicyLayer and add a rule for list_extensions: 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 list_extensions? +

list_extensions is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit list_extensions? +

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

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

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

Enforce policy on every Chrome DevTools tool call.

Start from Chrome DevTools, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →