A good interactive API documentation for your restful api is essential for the success and adaptation of the service / product. If apis are good and documentation sucks then no one would be able to consume apis easily.
Swagger is one of the best api documentation tool. Usually apis tools are read only monotonous api documentation, however swagger is much more interactive. Its try out feature is awesome and allows the actual call to apis with payload and query parameters and responds back in the real time.
Click this link and try doing CRUD operation on user – http://petstore.swagger.io/#/user
Swagger also has a WYSIWYG (what you see what you get ) editor for API documentation tool. It allows you to write and review and execute all at the same time. I loved it. So cool, simple and effective.