Knowledge-based systems (KBS) should be able to explain their results to improve the understanding and credibility of their answers by users. However, most KBS explanation components cannot be easily reused by other applications, thus increasing the effort of implementing KBSs with explanation capabilities. In this paper we present WebExplain, an extension to Unified Problem-Solving Method Description Language (UPML), a KBS development framework. WebExplain is integrated with UPML generic components and can be easily reused during the development of other problem-solving methods and KBSs. WebExplain uses the Inference Web for enabling proof and explanation interoperability between distributed applications. We exemplify our approach by describing WebExplain’s use in the development of a problem-solving method and a KBS with explanation capabilities.