He was the author, or more accurately the compiler, of the Golden Legend, a collection of the legendary lives of the greater saints of the medieval church that was one of the most popular religious works of the Middle Ages.

On the last occasion he was one of the four delegates charged with signifying Pope Nicholas IV's desire for the deposition of Munio de Zamora – who had been master of the Dominican order from 1285 and was eventually deprived of his office by a papal bull dated 12 April 1291.

Jacobus reached Rome on Palm Sunday (30 March), only to find his patron ill of a deadly sickness, from which he died on Good Friday (4 April).

The cardinals, however, propter honorem Communis Januae ("for the honor of the commune of Genoa"), determined to carry out this consecration on the Sunday after Easter.

For he compiled the legends of the saints (Legenda sanctorum) in one volume, adding many things from the Historia tripartita et scholastica, and from the chronicles of many writers.

"But," adds the historian of the Dominican order Jacques Échard, "if he did so, the version lies so closely hid that there is no recollection of it," and it may be added that it is highly improbable that the man who compiled the Golden Legend ever conceived the necessity of having the Scriptures in the vernacular.

[3] The Golden Legend, one of the most popular religious works of the Middle Ages,[9] is a collection of the legendary lives of the greater saints of the medieval church.

The saints' lives are full of fanciful legend, and in not a few cases contain accounts of 13th century miracles wrought at special places, particularly with reference to the Dominicans.

The sixth part deals with the constitution of the city, the seventh and eighth with the duties of rulers and citizens, the ninth with those of domestic life.

The tenth gives the ecclesiastical history of Genoa from the time of its first known bishop, Saint Valentine, "whom we believe to have lived about 530 A.D.", until 1133, when the city was raised to archiepiscopal rank.

The eleventh contains the lives of all the bishops in order, and includes the chief events during their episcopates; the twelfth deals in the same way with the archbishops, not forgetting the writer himself.