Web applications don't talk with front-end and database only anymore. They increasingly often talk with each other. In order not to get crazy in this communication mess, it’s good to take a look at many aspects of creating web API. We will answer the "why", "what" and "how" questions to begin with. We will meet the three wizards: Morville, Fielding and Richardson. We will play with resources, behavior, relations, parameters, headers, collections, versioning, errors, security, throttling, cache, HATEOAS, management performance, health and business. There will be a bunch of tips on how to make consumers of our API happy. Warning: may contain traces of snakes and camels.