Besides R&B, Wikipedia lists “Is It Cool?” as soul. The Steve Lacy song is presented as an R&B and soul track, with additional elements of funk in its production.
The genre label reflects the song’s blend of contemporary and classic influences. Its arrangement is built around a soft guitar line and a restrained beat, while SZA contributes subdued vocals, harmonies, a second verse, and the outro. Those choices give the track a smooth, intimate feel rather than the harder edge associated with rock or disco.
The song’s subject matter also fits its soulful presentation. Lacy sings about infidelity, self-sabotage, emotional immaturity, and the difficulty of building trust in a romantic relationship. SZA answers from the partner’s perspective, creating a conversational duet instead of a straightforward solo performance.
Listeners may be tempted to choose funk because the song contains funk elements, but funk is described as an influence rather than one of the two primary genres in the infobox. Likewise, “rock” and “disco” are not the Wikipedia genre labels for this recording. The canonical answer is soul.