install_extension

THE RISK

High Risk

Why install_extension needs a policy

Installing a browser extension executes an external operation that loads arbitrary code into the browser environment, granting it persistent access to browsing data, network requests, and page content. This is not a simple write (it actively runs/registers executable code) and is not easily reversible in terms of the damage a malicious extension could cause before removal.

From the tool's definition 'Installs a Chrome extension from the given path'

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

POLICY

How to control install_extension

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 install_extension:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "install_extension": {
      "limits": [
        {
          "counter": "install_extension_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

install_extension 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.

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.

RATE-LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Chrome DevTools tools

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All 50 Chrome DevTools tools →

Execute tools on other servers

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Go deeper

Govern code and CI agents → Branch allowlists, approval on merges, and rate caps on the build and pipeline tools agents trigger.
High-risk tools in Chrome DevTools → Every high-risk tool this server exposes, in one view.
All high-risk MCP tools → Every high-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
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 install_extension

What does the install_extension tool do? +

Installs a Chrome extension from the given path. 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 install_extension? +

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

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

Can I rate-limit install_extension? +

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

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

install_extension 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 →