How to add a dataclass field without annotating the type?

The dataclass decorator examines the class to find fields, by looking for names in __annotations__. It is the presence of annotation which makes the field, so, you do need an annotation.

You can, however, use a generic one:

@dataclass
class Favs:
    fav_number: int = 80085
    fav_duck: 'typing.Any' = object()
    fav_word: str="potato"