This is a small toad with wide, flat, spiny parotid glands. The dorsum is brown with light colored spines and variable darker markings. The upper lip is pale. This species lacks a tympanum. The legs are short (tibia less than ½ SVL). The ventral surface has some mottling (Text from Harper et al., 2010).
Tadpoles have a conspicuous circular crown that is thought to aid in respiration; a similar structure is found in the tadpoles of M. micranotis and M. taitana (Text from Harper et al., 2010).
M. usambarae is very similar to the other species in the genus, but the ventral surface is light with darker mottling and lacks the distinct chest spot, ventral stripe or black belly found in the other species (Text from Harper et al., 2010).
Males have snout-vent lengths up to 35 mm and females up to 45 mm (Harper et al., 2010).
M. usambarae is ecologically similar to M. micranotis, and the two species often occur together (Text from Harper et al., 2010).
This species is known only from the East Usambara foothills.
This species is found in lowland forest up to 410 m. It tolerates some degree of habitat degradation including selective logging (Harper et al., 2010).
Breeding behavior has not been observed (Harper et al., 2010).