Play Framework: How to define a writable object in scala?

Using Play, I have an object called RepositoryMetadata. I want to use that object in a method called post. The definition of that method is given below.

def post[T](body: T)(implicit wrt: Writeable[T], ct: ContentTypeOf[T]): Future[WSResponse].

How do I make the object RepositoryMetadata into Writeable.