On that point, after you've read whichever of the many great recommendations you end up reading, don't get discouraged if you end up having to scrap the first several APIs you build. Part of the reason building APIs is so opinionated is that it's so difficult to do it well. Look at the API documentation for a bunch of different Google projects. Some of them are absolutely abominable. Others are quite good. Algolia has great documentation. When you get it wrong, you'll know. And that's all you really need to make sure you do better next time.