Actions with the spellshape trait tweak the properties of your spells. You must use a spellshape action directly before casting the spell you want to alter. If you use any action (including free actions and reactions) other than casting a spell directly after, you waste the benefits of the spellshape action. Any additional effects added by a spellshape action are part of the spell's effect, not of the spellshape action itself.
Source: Player Core pg. 189
Trigger: An ally within 30 feet Casts a Spell
You rhyme with your ally’s incantations or echo their movements, linking your magic to empower their spell in one of two ways:
If their spell deals damage and doesn’t have a duration, you grant that spell a status bonus to damage equal to its rank.
If their spell doesn’t have a spellshape effect applied to it, apply the effects of any one spellshape feat you know to the spell. The spellshape feat must be one that can be applied to the triggering spell, and you must be able to use it (for instance, if the spellshape feat is usable only a limited number of times per day).
