Pelophryne api is only known from limestone outcrops in northern Sarawak (Gunung Mulu National Park).

It is a dark brown to black toad with lighter markings that may form faint dorsal and dorsolateral stripes. The legs are barred. The iris is mostly black, except for a small greenish-yellowish stripe in the upper and a similar smaller one in the lower iris, both neighboring the pupil. The webbing of hands and feet is fleshy, characteristic for the genus.

Size of adults: <20 mm snout-vent length.

Males call from limestone rocks of low vegetation with a high pitched call. Reproduction, diet, and ecology of this species are largely unknown. 

Tadpoles are unknown, however, we expect Pelophryne api to have a tadpole stage. These could be endotrophic as some other species of the genus Pelophryne.