Yes I think users putting either @Embeddable or @Emebedded should be sufficient to get going. Someone was not agreeing to me because it was not the letter of the spec, my main argument was ease of use and the fact that it is trivial to do.

That was me Personally I think we should have worked closer to the spec and enforce the @Embedded. I still believe it would be better, but of course we have also the issue of backward compatibility. If we want to be backwards compatible we need to extend CondifuredClass#determineAttributeNature. For the case that there is no annotation and it is not a basic type we need to check whether the type has an @Embeddable annotation. Should be straight forward. I discussed this with Strong Liu at our team meeting. He knows about it, but I am not sure whether he already has done something.

Inline classes are not being automatically added.

Correct. At the moment you would have to add it manually. We had a similar issue w/ (mapped) super classes. The place to fix this is MetadataSources#indexClass. There we should add for each added class also all inner classes. Class#getDeclaredClasses() should give you the information you need.