next · Rr MCP: Risk & Policy

WHAT IT DOES

What next does on Rr

AI agents invoke next 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 next needs a policy

This tool advances execution in a live debugging session by stepping over a function call. It triggers an external operation (controlling a running process via rr debugger), making it an Execute-category tool. Misuse could cause the debug session to advance past critical breakpoints or alter session state, though blast radius is limited to the debugging session itself.

From the tool's definition Step forward one source line, stepping over function

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

next Rate-limited

next 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": {
    "next": {
      "limits": [
        {
          "counter": "next_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 next

What does the next tool do? +

Step forward one source line, stepping over function. 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 next? +

Register the Rr MCP server in PolicyLayer and add a rule for next: 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 next? +

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

Can I rate-limit next? +

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

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

next 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.