I need a brief clarification on the spell dragon's breath (Xanathar's Guide to Everything, p. 154):
Until the spell ends, the creature can use an action to exhale energy of the chosen type in a 15-foot cone.
I think the description is ambiguous regarding the number of times you can exhale during the duration of the spell. You can think of that "an action" in 2 ways:
Until the spell ends, the creature can use one action to exhale magical energy. It can use an action this way as many times as it wants for the duration of the spell.
Until the spell ends, the creature can exhale magical energy once during the spell's duration, losing the ability to do so after that first time.
Which is the correct interpretation?