Mesh effect field

Do all these methods have to be written in my contentprocessor class or in a modified version of MGCB ?
And another question, why, when building the model to whom the effect.xnb will be assigned, is again passed into

public ExternalReference BuildAsset<TInput,TOutput>(
ExternalReference sourceAsset,
string processorName
)
{
return BuildAsset<TInput, TOutput>(sourceAsset, processorName, null, null, null);
}

I can’t figure why it is rebuilding another time an already xnb file.
Or is this a generic name to import data onto the mesh in the processor ?

So, (I’m using the sourcecode of monogame and its tools to find where the problem lies),
as it already is an effect built into an xnb, i used the debugger to manually set the importerName to “EffectImporter” into:

public PipelineBuildEvent BuildContent(string sourceFilepath, string outputFilepath = null, string importerName = null, string processorName = null, OpaqueDataDictionary processorParameters = null)
{
sourceFilepath = PathHelper.Normalize(sourceFilepath);
ResolveOutputFilepath(sourceFilepath, ref outputFilepath);
//TODO: Change importerName to “EffectImporter”, it will trigger a “Bad token CppNet.Token” exception (didn’t test if xnb is not something different from an effect file)
ResolveImporterAndProcessor(sourceFilepath, ref importerName, ref processorName);

And then it triggers “Bad token CppNet.Token” exception, same one as @Sizaar has bumped into: Custom model processor