Successful open source projects foster collaboration and innovation while benefiting from a faster pace of development, but are often plagued by poor developer?s documentation. In this paper, we present the rationale and the architecture of Mismar, a toolset tightly integrated in the Eclipse environment and implementing a concern-oriented approach to documentation. As opposed to traditional documentation artifacts, guides produced by Mismar are almost wordless and automatically maintain implementation examples. Moreover, since Mismar was built from the ground up to be extensible, it is easy to support artifacts written in multiple languages or modeling approaches.