Does the frame add useful signal?
Check object visibility, background level, transparency and whether the frame improves the stack.
FITS quality checklist for astrophotography frames.
Before stacking, ask whether the frames are sharp, consistent, aligned with the session goal and free from problems that will damage the final result.
Are stars round and usable?
Look for elongation, vibration, saturation, focus drift and changing star quality.
Does it match the session?
Exposure, filter, temperature, target position and metadata should make sense for the stack.