Tools are vital to support the various activities that form the many tasks that are part of the program comprehension process. In order for these tools to be used and useful, it is necessary that they support the activities of the user. This support must complement the work methods and activities of the user and not hinder them. Whilst features of good tools have been identified, tool builders do not always adhere to them. It is important to consider whether needs have changed, and if those desirable properties need augmenting or revising. From experience of maintaining and enhancing an existing program comprehension tool for the purposes of participating in a re-engineering activity, many lessons on tool support have been learned. Various program comprehension strategies are introduced in this paper. The use of GXL (Graph eXchange Language) and involvement in the SORTIE project are presented with reference to the tool being adapted and used. Details of the changes made are given to illustrate the support desired. These all feed into the final section of the paper that discusses the sort of support that tools should provide, current tool deficiencies and some of the ways in which these could be addressed.