What you may legally call it
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A vocabulary page, because in this craft the wrong adjective changes which agency regulates you.
Words carry the category
The soap exemption requires that the product be labeled, sold and represented only as soap.
So the claim is not a marketing layer on top of a settled product. It is one of the two conditions that decide the category.
Which means the copy, the label, the website and the market table sign are all part of the determination, and they have to agree with each other.
The words that keep the exemption
Soap. Bar soap. Cleans. Washes. A description of what is in it. A description of how it was made. The scent, named as a scent.
These say the product cleans and say nothing more, which is what the exemption requires.
Notice how narrow that is compared with how most handmade soap is actually sold.
The words that make it a cosmetic
Moisturizing. Nourishing. Softening. Gentle on skin. Anti-aging. Cleansing and conditioning.
Any claim to beautify, promote attractiveness or alter the appearance.
One of these anywhere in your representation and the exemption is gone, whatever the composition.
That is not a disaster. It means you label it as a cosmetic, which is entirely normal.
The words that make it a drug
Antibacterial. Antimicrobial. Treats acne. Relieves eczema. Heals. Kills germs. Anti-fungal.
Anything offered to treat or prevent disease, or to affect the structure or function of the body.
These are the expensive ones, and they are also the easiest to say by accident, particularly around tea tree, sulfur, and anything sold near a skin condition.
And note that an established name or a well-known intended use can carry the claim even when the label does not say it outright.