This issue is pointed in #40 by @roblabla and @MikKoz. Thanks for their report :-)
The point to fix is as follows(quoted from #40):

Javadoc:

• all annotations
• all interfaces (including, but not limited to, Template, TemplateBuilder, Packer, Unpacker, Value, MessagePackable, etc.)
• all "entry" classes, such as MessagePack,
• standard implementation classes, ones you would expect to occur in stacktraces often, such as AnyTemplate.