js_run · Ruyipage MCP: Risk & Policy

WHAT IT DOES

What js_run does on Ruyipage

AI agents invoke js_run to trigger actions in Ruyipage. 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 js_run needs a policy

A tool that runs JavaScript in a browser context is an Execute action with critical severity. Even without explicit description, 'js_run' in a browser automation server means arbitrary code execution, which has maximal blast radius—an AI agent could exfiltrate data, manipulate the DOM, perform unauthorized transactions, or pivot to other systems via the browser environment.

From the tool's definition Tool name 'js_run' indicates execution of arbitrary JavaScript; server context shows Firefox browser automation; tool description is empty but the name combined with server purpose strongly implies code execution capability.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

js_run Rate-limited

js_run 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": {
    "js_run": {
      "limits": [
        {
          "counter": "js_run_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 Ruyipage, so you can run agents against it safely.

FAQ

Questions about js_run

What does the js_run tool do? +

js_run. It is categorised as a Execute tool in the Ruyipage MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on js_run? +

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

What risk level is js_run? +

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

Can I rate-limit js_run? +

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

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

js_run is provided by the Ruyipage MCP server (neverl805/ruyipage_mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.