In Arabic, waṣf can mean a descriptive dependent expression (roughly a naʿt) or the act of describing, that is, the verbal-noun sense. The latter better fits the sequence describing what the speaker does with the subject.
وَالْوَصْفُ قَدْ يُطْلَقُ عَلَى نَفْسِ التَّابِعِ الْمَخْصُوصِ، وَقَدْ يُطْلَقُ بِمَعْنَى الْمَصْدَرِ
Waṣf may denote the particular dependent expression or the verbal act of description.
This prevents reducing the rhetorical discussion to the syntactic definition of a naʿt. The aim is to understand why the subject has been qualified in a particular way.