Service descriptions allow designers to document, understand, and use services, creating new useful and complex services with aggregated business value. Unlike RPC-based services, REST characteristics require a different approach to service description. We present the Resource Linking Language (ReLL) that introduces the concepts of media types, resource types, and link types as first class citizens for a service description. A proof of concept, a crawler called RESTler that crawls RESTful services based on ReLL descriptions, is also presented. Categories and Subject Descriptors H.3.5 [Information Storage and Retrieval]: Online Information Services—Web-based services, Data sharing General Terms Design, Documentation, Languages Keywords REST, Web Services, SOA, Crawling