Prefer Top-Level Functions for Business Logic Entry Points

Goal

When implementing a business-logic entry point, prefer a top-level function over a class or object, as long as the project stack allows it without introducing friction.

A top-level function is a function defined at module scope, not inside a class or object. It is the simplest code shape for an entry point: one function, one module, no wrapper.

What Counts as In Scope

Apply this skill to code that does one or more of these things:

• defines a new business-logic entry point and must choose between a top-level function, a class, or an object
• wraps a single entry-point function in a class or object without a clear reason
• uses a class or object only as a container for one public method plus dependency injection that could be achieved with function parameters or closures

The Rule