This article introduces an objective API Style Guide that has a strong architectural foundation, aiming to eliminate friction in API development lifecycle. It covers important points to consider when modelling an API operation, such as applying architectural patterns outside-in, avoiding exposing the entire domain model in the API interface, and keeping the protocol layer isolated from the domain model. The article emphasizes the significance of a consistent and credible API style guide for developing APIs, and how it can facilitate the learning and practicing of architectural patterns that promote objective and consistent thinking.