tracing_stop · MCP Playwright Server MCP: Risk & Policy

WHAT IT DOES

What tracing_stop does on MCP Playwright Server

AI agents invoke tracing_stop to trigger actions in MCP Playwright Server. 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 tracing_stop needs a policy

This tool executes a browser tracing operation (stopping an active trace recording) and commits its output to disk. While the immediate action (stopping a trace) is not itself destructive or dangerous, it is a triggered operation that modifies system state (creates/writes a file) and depends on prior browser context state.

From the tool's definition Tool name 'tracing_stop' combined with 'save the trace to a file' indicates it performs a filesystem write operation as part of web browser automation control. The server description confirms this is part of 50+ automation tools for browser control.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

tracing_stop Rate-limited

tracing_stop 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": {
    "tracing_stop": {
      "limits": [
        {
          "counter": "tracing_stop_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 MCP Playwright Server, so you can run agents against it safely.

FAQ

Questions about tracing_stop

What does the tracing_stop tool do? +

Stop recording and save the trace to a file. Open the trace file at https://trace.playwright.dev. It is categorised as a Execute tool in the MCP Playwright 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 tracing_stop? +

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

What risk level is tracing_stop? +

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

Can I rate-limit tracing_stop? +

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

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

tracing_stop is provided by the MCP Playwright Server MCP server (j0hanz/playwright-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.