This tool is used to bring API docs generated by Doxygen on Objective-C APIs into a MonoTouch or Xamarin.Mac binding being documented with Mono's documetation pipeline.
To use, first make sure your doxygen.config is setup to generate XML documentation, by setting the GENERATE_XML variable to YES. Then run doxygen:
doxygen myDoxygen.config
That will generate an "xml" directory with the docs. If you have not generated your docs, run:
mdoc update Foo.dll -out:Docs
Then import the doxygen docs into a MonoDoc maintained
mono DoxyToEcma.exe ECMA_DIR DOXY_DIR