Documenting TableGen searchable tables

It has been suggested that I document the TableGen searchable tables classes in detail. Currently, there is some documentation in, and there are a couple of Doxygen comments in the backend, SearchableTableEmitter.cpp.

My question: Is it a good idea to add a large appendix to the new TableGen Programmer's Reference and so end up with documentation in two places, or is it better to improve the documentation in the .td and .cpp files?