For the duration, you sense the presence o f magic within 30 feet of you. If you sense magic in this way, you can use your action to see a faint aura around any visible creature or object in the area that bears magic, and you learn its school of magic, if any. [...]
If this spell is used in presence of a magical item, does the aura assume the exact shape of the item, or just a general shape? The question can be read as: is the caster able to guess the item's shape by just seeing the aura?