For messages sent from Compose, Chat, Recurring and Sequences, Sprwt sends exactly what you type — no footer is added — so include opt-out wording in promotional texts yourself (the registered campaign samples show the expected style). Texts sent through the separate Marketing Campaigns feature are different: there Sprwt automatically appends "Reply STOP to opt out" (plus the campaign's privacy and terms links) unless the body already contains "STOP".