Those examples in the article are what I would consider APIs. It is just that it is written in a way that is _composable_, and the primitives are scoped in a wa

Those examples in the article are what I would consider APIs. It is just that it is written in a way that is _composable_, and the primitives are scoped in a way that composing them versatile. That there was a library that facilitates that composition allows for an ecosystem. The Rack protocol did something similar for http servers in the Ruby world, allowing for a number of middleware. Whole frameworks (Rails, Sinatra, as examples) could be mounted on specific routes.