js_preload · Ruyipage MCP: Risk & Policy

WHAT IT DOES

What js_preload does on Ruyipage

AI agents invoke js_preload 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_preload needs a policy

The 'js_' prefix strongly implies JavaScript execution in the browser. In the context of a Firefox browser automation MCP server, preloading JavaScript likely means injecting or executing scripts before page load, which is an Execute-category action with high blast radius potential. Confidence is reduced due to the empty description.

From the tool's definition Tool name 'js_preload' suggests JavaScript preloading/execution in a browser context; description is empty and uninformative.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

js_preload Rate-limited

js_preload 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_preload": {
      "limits": [
        {
          "counter": "js_preload_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_preload

What does the js_preload tool do? +

js_preload. 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_preload? +

Register the Ruyipage MCP server in PolicyLayer and add a rule for js_preload: 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_preload? +

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

Can I rate-limit js_preload? +

Yes. Add a rate_limit block to the js_preload 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_preload completely? +

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

js_preload 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.