browser_install · Playwright MCP: Risk & Policy

WHAT IT DOES

What browser_install does on Playwright MCP

AI agents invoke browser_install to trigger actions in Playwright 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.

WHY IT NEEDS A POLICY

Why browser_install needs a policy

Installing a browser involves executing system-level operations (downloading binaries, writing to disk, modifying system state). This is an Execute action with high severity since it installs software on the host system, which could have significant side effects and blast radius if misused.

From the tool's definition Install the browser specified in the config. Call this if you get an error about the browser not being installed.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

browser_install Rate-limited

browser_install 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": {
    "browser_install": {
      "limits": [
        {
          "counter": "browser_install_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Playwright MCP, so you can run agents against it safely.

FAQ

Questions about browser_install

What does the browser_install tool do? +

Install the browser specified in the config. Call this if you get an error about the browser not being installed. It is categorised as a Execute tool in the Playwright 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 browser_install? +

Register the Playwright MCP server in PolicyLayer and add a rule for browser_install: 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 Playwright MCP. Nothing to install.

What risk level is browser_install? +

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

Can I rate-limit browser_install? +

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

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

browser_install is provided by the Playwright MCP server (nzjami/mcpplaywright). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.