run_js_interaction · Nav MCP: Risk & Policy

WHAT IT DOES

What run_js_interaction does on Navmcp

AI agents invoke run_js_interaction to trigger actions in Navmcp. 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 run_js_interaction needs a policy

This tool executes arbitrary JavaScript in a browser, making it Execute-class with critical severity due to unrestricted code execution capability that could exfiltrate data, modify page content, interact with sensitive elements, or trigger unwanted actions. The empty description raises concerns about lack of documented constraints.

From the tool's definition Tool name 'run_js_interaction' indicates execution of JavaScript code in a browser context. Server description confirms 'browser automation' via Selenium.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

run_js_interaction Rate-limited

run_js_interaction 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": {
    "run_js_interaction": {
      "limits": [
        {
          "counter": "run_js_interaction_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 Navmcp, so you can run agents against it safely.

FAQ

Questions about run_js_interaction

What does the run_js_interaction tool do? +

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

How do I enforce a policy on run_js_interaction? +

Register the Nav MCP server in PolicyLayer and add a rule for run_js_interaction: 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 Navmcp. Nothing to install.

What risk level is run_js_interaction? +

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

Can I rate-limit run_js_interaction? +

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

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

run_js_interaction is provided by the Nav MCP server (jianlins/navmcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.