At my company, we've been very happy using WADL, Web Application Description Language. Wikipedia describes it as: "an XML-based file format that provides a machine-readable description of HTTP-based web applications". I find raw WADL easy to write, read, and understand, and it maps directly to RESTful concepts. The official project provides a simple spec, XSD and RELAX NG schemata, and Java tools.
A number of tools and resources exist for working with WADL, including:
- wadl_stylesheets, XSLT stylesheets to create HTML documentation from WADL files
- Restlet, a Java framework for building RESTful servers and clients, includes a WADL extension
A tip: try including human-readable documentation, such as descriptions, concepts, getting started, usage tips, etc, in the WADL document's doc element by including HTML elements, using the XHTML namespace. It can make a big difference!
