At Twelve Data, we have a lot of experience in creating various APIs. Some of these tips have been gained through practical errors. We would like to share with you some of them that we ourselves are following in order to make it easier to develop and maintain our own product in the future.
Versioning
From the very beginning of the development of your API, no matter how small it may seem to you, take versioning into an account in your architecture. If you don't want to write code to support versioning right away, then at least try to agree on how you will do it in the future. At the very least, you need to be prepared for this.