Agalychnis annae is a moderately large and slender frog. Males have a maximum snout-vent length of 73.9 mm, and females 84.2 mm. The head is slightly convex and is narrower than the body. Males have a softly sloping snout from the eyes to the nostrils in lateral profile. Females have a blunt snout in lateral profile (Duellman 2001). The eyes are large and the lower eyelid is reticulate. The dorsal surface is smooth and the venter is faintly granulate (Savage 2002). The tympanum is distinct, besides the upper and posterior edges which are covered by a heavy dermal fold. This fold extends from the posterior corner of the orbit to a point posterior to the angle of the jaw. A narrow dermal fold also extends from the elbow along the ventrolateral edge of the forearm onto the base of the fourth finger. A weak tarsal fold is observed along the entire length of the tarsus. Another thin dermal fold is present from the heel along the ventrolateral edge of the tarsus to the fifth toe. The upper arm is slim and the forearm robust, while the hind limb is slender. The fingers of A. annae are short with large discs. The diameter of the disc on the third finger is equal to that of the tympanum. The toes are somewhat slim and the terminal discs are only slightly smaller than those on the hand. Fingers are about 2/3 webbed and toes are webbed (Duellman 2001). There is a brown nuptial pad on the base of the thumb in adult males (Savage 2002). The vocal sac is unpaired, median, subgular and not markedly distensible (Duellman 2001). This frog is quite colorful. In contrast to the uniform green upper surfaces, the proximal dorsal portion of the upper arm is pink to lavender and the distal portion is blue. The flanks and anterior and posterior thigh surfaces are blue. The upper surface of the hands and feet are green, orange, and blue. There are vivid creamy yellow stripes along the ventrolateral margin of the forearm, tarsus and foot. The venter is creamy yellow to orange. This species is able to undergo metachrosis (color change), and the colors darken at night to a darker green and bluish purple. Metamorphs lack blue coloring and turn reddish brown at night and in preservatives (Savage 2002). Larvae are moderately sized and have a total length of 33 mm at stage 31. The eyes are dorsolateral and directed laterally and the nostrils are dorsolateral and directed anterolaterally. The tail is moderate, caudal fins are high and the tail tips are short. The oral disc is small and entire, with large, serrated beaks and 2/3 rows of denticles. The mouth is located anteroventrally and directed anteriorly. Papillae border the mouth in two rows and laterally scattered small papillae lie medially to the fringing row. The spiracle is ventral and sinistral to the midline (Duellman 2001). Tadpoles have a heavily pigmented snout, top of head, and body, appearing grayish brown. The sides of the body are bluish gray, and the venter is light blue-gray with a silvery cast. The larval caudal musculature is a light gray brown. The caudal fins are clear with brown dashes on the proximal edges of the anterior half of the dorsal and ventral fins. During development, the pigmentation increases on the dorsal surface of the body and the caudal musculature, while the pigment in the caudal fins decreases. The iris is yellow (Duellman 2001).