The sandbox's roll() only accepted notation, but build_tool_signatures() advertised the MCP version's signature which includes reason — so the DM tried passing reason and got a TypeError. Now _roll_host accepts reason too (ignores it, it's only for the CLI notification). Also cleaned up the run_code tool description: dropped the false claim that random is available (it's not in Monty), spelled out clearly that roll() -> dict while all other tools -> str, and showed how to use the dict keys for math. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>