browser_run_code · Playwright MCP: Risk & Policy

WHAT IT DOES

What browser_run_code does on Playwright MCP

AI agents invoke browser_run_code 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_run_code needs a policy

A tool named 'browser_run_code' with no description but situated within a Playwright MCP server that performs browser automation is classified as Execute. The ability to run code in a browser context is an Execute risk because it triggers external operations (JavaScript execution) whose effects depend entirely on the arguments supplied.

From the tool's definition Tool name 'browser_run_code' combined with server context describing browser automation capabilities indicates execution of arbitrary code within a browser context.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

browser_run_code Rate-limited

browser_run_code 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_run_code": {
      "limits": [
        {
          "counter": "browser_run_code_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_run_code

What does the browser_run_code tool do? +

browser_run_code. 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_run_code? +

Register the Playwright MCP server in PolicyLayer and add a rule for browser_run_code: 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_run_code? +

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

Can I rate-limit browser_run_code? +

Yes. Add a rate_limit block to the browser_run_code 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_run_code completely? +

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

browser_run_code is provided by the Playwright MCP server (roshan571/playwright-mcp2). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.