start_codegen_session

THE RISK

High Risk

Why start_codegen_session needs a policy

This tool triggers external operations (browser automation and code generation recording) whose effects depend on subsequent user actions and arguments. While not immediately destructive or financial, it enables the execution of arbitrary browser commands and JavaScript in a real browser context.

From the tool's definition Tool description states it 'record[s] Playwright actions' within 'a real browser environment' where users can 'execute JavaScript'.

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

POLICY

How to control start_codegen_session

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

policy.json

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

start_codegen_session 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 Playwright MCP Server — 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 Playwright MCP Server tools

Destructive clear_codegen_session Clear a code generation session without generating a test Destructive playwright_close Close the browser and release all resources Execute playwright_delete Perform an HTTP DELETE request Execute playwright_evaluate Execute JavaScript in the browser console Execute playwright_expect_response Ask Playwright to start waiting for a HTTP response. This tool initiates the wait operatio Execute playwright_navigate Navigate to a URL Execute playwright_click Click an element on the page Execute playwright_custom_user_agent Set a custom User Agent for the browser

All 29 Playwright MCP Server tools →

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Go deeper

High-risk tools in Playwright MCP Server → 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 →

FAQ

Questions about start_codegen_session

What does the start_codegen_session tool do? +

Start a new code generation session to record Playwright actions. It is categorised as a Execute tool in the Playwright MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on start_codegen_session? +

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

What risk level is start_codegen_session? +

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

Can I rate-limit start_codegen_session? +

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

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

start_codegen_session is provided by the Playwright MCP Server MCP server (pvinis/mcp-playwright-stealth). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Playwright MCP Server tool call.

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

CHECK YOUR STACK →