The large silver statue of St. James Enthroned by Giglio Pisano was added in 1349, and in 1361, the sides of the altar were enlarged. The left side was finished in 1364 by Florentine goldsmiths Francesco Niccolai and Leonardo di San Giovanni, while the right side vaunts nine scenes from the life of St. James cast by Leonardo di San Giovanni.
In 1386, the goldsmith Piero d'Arrigo Tedesco worked on the altar, while in 1394-1398, the painter Giovanni di Bartolomeo Cristiani designed the cornice of the reredos, cast by the Florentine goldsmith Nofri di Buto and Atto di Piero Braccini from Pistoia.
In the 15th century, the workshop of Lunardo di Mazzeo and Piero di Giovanni da Pistoia worked on the altar, including a young Filippo Brunelleschi, who is said to have sculpted the busts of the prophets Jeremiah and Isaiah, St. Augustine and St. John the Evangelist. Niccolò di Ser Guglielmo, Domenico da Imola and Piero d'Antonio da Pisa ultimately finished the altar.