There is a thread over in the archived forums that got right to the edge of addressing my problem:
I'm working in an ArcGIS 9.3.1 environment.
I have a Custom Geoprocessing Tool developed in VB.NET / Visual Studio 2005. It runs great in Desktop applications on the machine it was compiled on. I'm having trouble getting the map, toolbox, models and DLL containing the custom tool to all play nice on our ArcGIS Server. I've copyed the compiled DLL and related files to the server and registered the DLL using Regasm.exe. I do not have ArcGIS Desktop tools on the Server. Is there a special folder the custom tool needs to be placed in?
When I run a very simple model that only contains the custom tool I get the error:
000816 : The tool is not valid.
The archived thread ended tantalizingly with Matt Rodriguez stating: "I made this work. I had to ask ESRI developers for help because there isn't really documentation on how to do this."
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