Frogs in the genus Callulina are endemic to the Eastern Arc Mountains of Tanzania. They are characterised by short blunt snouts and plump bodies covered with glandular warts. Callulina stanleyi has a snout-to-vent length of . The dorsal surface is mainly brown with symmetrical darker brown or black streaks. The body is covered with granulations, and the larger glandular masses are pale tan, as are the underparts. It has expanded tips to its fingers and toes, and these help to distinguish it from other similar species, Callulina dawida, Callulina laphami and Callulina shengena. It also differs from C. laphami and C. shengena by having visible tympani. It is very close morphologically to Callulina kisiwamsitu, but it can be told from that species by its call and by DNA analysis.