Writing an API isn't the problem - being a perfectionist about internal design is.
My design process has gone from "write code that does something" to "figure out what data you want to store and how to validate it, then write code".
Once the data is in a defined format, it's much easier to change how the code works without breaking things. That's the way to go about API design - designing callable libraries that work in only one language and have only one implementation is a quick way to cut off a huge swath of developers from interacting with you.
Reminds me of one of the dev managers at my first "real job" -- this was in the 1990s -- who would say "get the data model right, and the code will almost write itself" and I have found in most cases (certainly for most "business" apps) that is true.
My design process has gone from "write code that does something" to "figure out what data you want to store and how to validate it, then write code".
Once the data is in a defined format, it's much easier to change how the code works without breaking things. That's the way to go about API design - designing callable libraries that work in only one language and have only one implementation is a quick way to cut off a huge swath of developers from interacting with you.