We developed a model that uses ArcHydro tools. It runs successfully on the desktop, but we cannot publish it as a geoprocessing service. The error we receive is �??000816 �?? Tool is invalid error�?�. Is it possible to use ArcHydro tools in a published geoprocessing service? If so, is there some additional configuration that makes it possible? The ESRIRegAsm tool was used to register dlls on the ArcGIS Server machine and all permissions have been set-up. Has anybody been able to use ArcHydro tools this way?