I think the perfect engineering is to build two pieces: the data functionality should be built into a CLI tool that could potentially be triggered by a human or

I think the perfect engineering is to build two pieces: the data functionality should be built into a CLI tool that could potentially be triggered by a human or other third party software, and then build a UI on top that mainly interacts with the CLI. Essentially this is the MVC pattern we nowadays mainly talk about in a web context.