Sano di Pietro is an exact contemporary of Giovanni di Paolo and a late representative of the International Gothic style. After studying under Sassetta, this easel painter and miniaturist headed a major workshop whose output proved both prolific and highly popular. His early youthful work has on occasion been mistaken for the work of the Master of the Observance. Like many Sienese artists, he incorporated contemporary artistic changes and owed much to 14th-century Gothic culture.

This mid-15th-century Annunciation to the Shepherds dates from the mature period of Sano di Pietro. It was painted at the pinnacle of a polyptych, as indicated by the angel’s gesture referring to a scene below, undoubtedly that of the Nativity. The balanced composition echoes the pointed arch imposed by the piece.

With an amiable and artificial narrative verve, the painter describes an angel announcing the Messiah's birth to the shepherds – that is to say, the poorest members of society – bearing an olive branch that heralds the advent of peace. In the late mediaeval imagination, the theme presents an opportunity to portray a human and familiar scene, shorn of its sacredness or solemnity. The profane and anecdotal atmosphere is borne out by the seated shepherds, barely surprised by the event, coupled with the outstretched muzzle of the curious dog or the detail of the enclosure with its few sleepy sheep.

Caught between prosaic truth and artificial preciousness, the work naively subscribes to the spirit of International Gothic and is reminiscent of the art of illumination. As permitted by their marginal position on a polyptych, the lateral scenes feature some interesting innovations. The golden background is abandoned in favour of a landscape with Tuscan accents, a sky of shaded colours and scattered clouds that testify to a desire to convey the ephemeral immediacy of visual perception. The issue of atmospheric perspective is reflected in the barely sketched towers and the muted colours behind the hills. This panel is a contemporary of the previous painting, the Virgin of Humility by Giovanni di Paolo but its approach to the landscape is more reminiscent of the endeavours of Renaissance artists. Indeed, the characters and motifs are fully integrated into a space that generously accommodates them. The landscape is no longer presented as the crow flies, resulting in a lower skyline and thus a more rational cityscape.