Usefulness is about the general usefulness of a project, not design. UX and DX ( you removed halve), it can be an API. An API doesn't need design or UX. There

Usefulness is about the general usefulness of a project, not design. UX and DX ( you removed halve), it can be an API. An API doesn't need design or UX. There's not a single absolute requirement on design. Since product design/ux is about graphics/visuals.