[1] H. agilis are slender and mainly black in colour, with distinctive yellow or white markings on their face.

[2] As found in all Hylaeus bees they lack pollen-carrying hairs (scopa), and resemble wasps.

Antennae are light brown on the ventral region to the pedicel; 1/3 to 2/5 of the outer pronotum is yellow.

The clypeus is characterised as flat and short; it extends for approximately 1/7th of its length below a line that runs across the lower margins of the compound eyes.

The face below the antennal sockets is characterised as shiny, tessellated lightly and has small punctures that are separated by 4-8 diameters (except the lower margin of the clypeus and the supraclupeus[ε]).

[4] The pronotum has irregular striae on lateral areas which are angled down and back by approximately 30° and are slightly tessellated.

The compound eyes are approximately 3x longer than they are wide; inner margins are similar to those found in females.

The supraclypeus[ν] rises from below to a small rounded point found between the antennal sockets[ξ] .

The facial fovea[A] is barely discernable, a short linear depression near the upper inner margin of the compound eye.

The clyepus is slightly rounded in cross-section, short, and extends for approximately 1/9th of its length below a line found across the lower margins of the compound eyes.

The rest of the head is similar to that found in females, however the face above the antennae shows dense tessellation.

[5] The mesosoma is similar to that found in females, however the propodeal triangle is slightly angled as opposed to rounded.

Metasomal terga 1-5[A] and sterna 1-5 are close to those found in females, except show more pronounced punctuation.

Gonostyli[A] are short, blunt and stout with hairs from the inner, apical and lateral faces.

[5] The pronotal angle of males can range from black to the yellow found typically in females.

The cellophane-like material adheres to the hole, and so the shape of nests mimics the cavity that they are made in.

[8] This species has been observed visiting Alepis flavida (yellow mistletoe), prying open the tips of buds and pushing down inside the tubes.

[8] H. agilis are also known to open Peraxilla tetrapetala (red mistletoe) flowers in order to feed from them, which has been recorded as improving fruitset.