reverse_nexti · Rr MCP: Risk & Policy

WHAT IT DOES

What reverse_nexti does on Rr

AI agents invoke reverse_nexti to trigger actions in Rr. 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 reverse_nexti needs a policy

This tool executes a reverse debugging step operation, triggering external process control in an rr debugging session. It actively manipulates the execution state of a running/replaying process, making it an Execute-category action. Misuse could disrupt debugging sessions or cause unintended process state changes, warranting medium severity.

From the tool's definition Step backward one machine instruction, stepping over calls in reverse

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

reverse_nexti Rate-limited

reverse_nexti 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": {
    "reverse_nexti": {
      "limits": [
        {
          "counter": "reverse_nexti_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 Rr, so you can run agents against it safely.

FAQ

Questions about reverse_nexti

What does the reverse_nexti tool do? +

Step backward one machine instruction, stepping over calls in reverse. It is categorised as a Execute tool in the Rr MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on reverse_nexti? +

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

What risk level is reverse_nexti? +

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

Can I rate-limit reverse_nexti? +

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

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

reverse_nexti is provided by the Rr MCP server (jnjaeschke/rr-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.