ToolScope

The call a Tool.scoped handler is serving, given to the handler and nowhere else: reject, ensure, ?, ToolScope.call and ToolScope.idempotencyKey need one, so using them outside a scoped handler does not compile.

reject ends the call with scala.util.boundary's break, which is an exception the handler's own Try or catch NonFatal would catch: do not wrap a call to reject, ensure or ? in either. Nor keep the scope after the handler returns, or use it on another thread: the call has then ended, and there is nothing to end.