har_record_start · MCP Playwright Server MCP: Risk & Policy

WHAT IT DOES

What har_record_start does on MCP Playwright Server

AI agents invoke har_record_start 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 har_record_start needs a policy

This tool triggers active recording of network traffic, which is an initiated operation that modifies the state of the browser session. It qualifies as Execute rather than Read because it isn't passive data retrieval—it starts a recording session with continuing side effects.

From the tool's definition Tool starts recording of network requests/HAR (HTTP Archive), which initiates an external operation with side effects (network capture session begins).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

har_record_start Rate-limited

har_record_start 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": {
    "har_record_start": {
      "limits": [
        {
          "counter": "har_record_start_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 har_record_start

What does the har_record_start tool do? +

Start recording HTTP Archive (HAR) for network analysis. Records all network requests during the session. 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 har_record_start? +

Register the MCP Playwright Server MCP server in PolicyLayer and add a rule for har_record_start: 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 har_record_start? +

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

Can I rate-limit har_record_start? +

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

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

har_record_start 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.