Many　iStar-based　modeling　and　analysis　tools　have　been　developed　for　specific　iStar-related　purposes　(e.g.,　tools　enumerated　in　iStar　wiki).　Despite　the　proliferation　of　tools,　new　tools　keep　being　built,　taking　resources　and　time　and　possibly　＇reinventing　the　wheel＇　in　terms　of　tool　functionality.　To　gain　an　in-depth　understanding　of　this　situation,　we　are　interested　in　the　challenges　and　tradeoffs　in　creating　iStar　tools.　In　this　paper,　we　examine　three　diverse　tools　as　case　studies,　illustrating　the　challenges　and　tradeoffs　from　the　developer＇s　perspective.　Based　on　such　studies,　we　establish　a　goal　model　to　capture　the　collected　knowledge,　which　can　help　researchers　to　make　informed　decisions　and　optimize　their　tool　development.　Copyright　©　2016　for　this　paper　by　its　authors.