start_session · gdb and rr Debugging MCP: Risk & Policy

WHAT IT DOES

What start_session does on gdb and rr Debugging

AI agents invoke start_session to trigger actions in gdb and rr Debugging. 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 start_session needs a policy

While start_session itself only initializes a session and does not directly execute code, it is a foundational Execute action that enables the full suite of code execution tools (run, exec_command) on this server. An AI misusing this could gain the ability to execute arbitrary programs and inspect/modify their runtime state.

From the tool's definition Tool 'start_session' initializes a GDB debugging session, which enables subsequent tool calls to 'run', 'exec_command', and other debugging operations that execute arbitrary code.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

start_session Rate-limited

start_session 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": {
    "start_session": {
      "limits": [
        {
          "counter": "start_session_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 gdb and rr Debugging, so you can run agents against it safely.

FAQ

Questions about start_session

What does the start_session tool do? +

Start a new GDB session. Returns session_id for all other tools. It is categorised as a Execute tool in the gdb and rr Debugging MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on start_session? +

Register the gdb and rr Debugging MCP server in PolicyLayer and add a rule for start_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 gdb and rr Debugging. Nothing to install.

What risk level is start_session? +

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

Can I rate-limit start_session? +

Yes. Add a rate_limit block to the start_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 start_session completely? +

Set action: deny in the PolicyLayer policy for start_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 start_session? +

start_session is provided by the gdb and rr Debugging MCP server (schuay/gdb-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.