We studied a collection of 32 publically published guide-lines for designing RESTful Application Programming In-terfaces (APIs), each from a different company, to identify similarities and differences to see if there are overall best practices across ten different topics. Our contribution in-cludes providing a list of topics that API authors can refer-ence when creating or evaluating their own guidelines. Ad-ditionally, we found that while some guidelines attempt to enforce consistency, simplicity, and intuitiveness in the APIs that use these guidelines, cross-guideline comparisons show a lack of consistency in some of the topics examined, and different interpretations of what is thought to be “sim-ple” and “intuitive.”