The artist followed the Sienese tradition, which preferred linear grace and gold backgrounds. His work shows the influence of Simone Martini and the Lorenzetti brothers. Vanni often placed figures within architectural frames, such as the initial letters found in his missal fragments. These fragments demonstrate his ability to depict religious scenes, like the Ascension or the celebration of the Mass, within the confines of a single letter. He used a palette of blues and golds to create a sense of sacred space.

Modern collectors value these works for their graphic quality and historical detail. The fragments of missals provide a window into fourteenth-century religious life and book production. Because these pieces were originally part of larger volumes, they possess a portable and intimate quality. They suit contemporary interiors that favour historical objects with clear lines and distinct colours. The focus on single figures or specific scenes allows for a focused aesthetic in a home gallery.