step_out · MCP JS Debugger MCP: Risk & Policy

WHAT IT DOES

What step_out does on MCP JS Debugger

AI agents invoke step_out to trigger actions in MCP JS Debugger. 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 step_out needs a policy

This tool controls debugger execution flow by stepping out of a function, which is an active operation that triggers external debugger behavior. It doesn't read, write, or destroy data, but it executes a debugger control action affecting the running program's state.

From the tool's definition Steps out of the current function and pauses at the calling code

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

step_out Rate-limited

step_out 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": {
    "step_out": {
      "limits": [
        {
          "counter": "step_out_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 JS Debugger, so you can run agents against it safely.

FAQ

Questions about step_out

What does the step_out tool do? +

Steps out of the current function and pauses at the calling code. It is categorised as a Execute tool in the MCP JS Debugger MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on step_out? +

Register the MCP JS Debugger MCP server in PolicyLayer and add a rule for step_out: 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 JS Debugger. Nothing to install.

What risk level is step_out? +

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

Can I rate-limit step_out? +

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

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

step_out is provided by the MCP JS Debugger MCP server (johngrimes/mcp-js-debugger). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.