Map which Chapter 8 bases apply, then show the need is daily and can be met only in a SNF (the practical-matter test). This is what a coverage reviewer looks for on a Part A day.
Management & evaluation of the care plan
When psychosocial factors complicate recovery and require an RN to integrate them into the plan and keep the skilled care achieving its purpose, management and evaluation is itself the skilled service.
Teaching & training; observation & assessment
Teaching a caregiver to competence for a safe discharge is a covered skilled service, and observing a mood/engagement change that affects the skilled course requires nursing judgment.