set_active_session · Rn Debug MCP: Risk & Policy

WHAT IT DOES

What set_active_session does on Rn Debug

AI agents use set_active_session to create or update resources in Rn Debug — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Rn Debug environment.

WHY IT NEEDS A POLICY

Why set_active_session needs a policy

This tool modifies the active debugging session state, which is a reversible configuration change. It does not execute arbitrary code, delete data, or move money. While it can affect subsequent operations (since omitted sessionId parameters will use this session), the tool itself performs a Write operation by changing which session is active.

From the tool's definition Tool name 'set_active_session' and description 'Set the active session used when sessionId is omitted' indicate modification of session state. The word 'Set' and 'active session' explicitly show this changes configuration/state.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_active_session Rate-limited

set_active_session stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "set_active_session": {
      "limits": [
        {
          "counter": "set_active_session_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Rn Debug, so you can run agents against it safely.

FAQ

Questions about set_active_session

What does the set_active_session tool do? +

Set the active session used when sessionId is omitted. It is categorised as a Write tool in the Rn Debug MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on set_active_session? +

Register the Rn Debug MCP server in PolicyLayer and add a rule for set_active_session: 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 Rn Debug. Nothing to install.

What risk level is set_active_session? +

set_active_session is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit set_active_session? +

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

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

set_active_session is provided by the Rn Debug MCP server (rn-debug-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.