The point of annotations - to be able to annotate foreign modules. I can't force DBI author, for example, to annotate his methods with return values or use any signatures.

But to make my work more comfortable and faster, I'd like to have completion and navigation wherever possible.

With described approach, I can make file with annotations for any module and get it.

And plugin supports default perl signatures and Method::Signatures::Simple and know how to work with them.