The article emphasizes that APIs should be designed with humans in mind, not machines. It highlights the importance of making the common case easy, simplifying the surface area of the API, and being mindful of backwards-incompatible changes. The author shares examples from their own experience designing APIs for Twilio, such as the AvailablePhoneNumbers resource, which had to balance competing requirements and simplify its design over time. The article also stresses the need for transparency when making changes to an API, using client libraries to abstract away complexities and make it easier for users to upgrade. Ultimately, the goal is to build APIs that are easy to use, maintain, and extend, serving human developers who need to get things done.