A favourite pupil of Raffaello Caverni at Firenzuola, Tommasi embodied the young man to whom Caverni dedicated his short work Dell’arte dello scrivere, published first in instalments in the journals “La scuola”, “Ateneo” and “Letture di famiglia”. He started out, while he was still a student with the Piarists, with a volume of poems, Le prime viole, for which Caverni wrote a preface and which was dedicated to Pietro Fanfani. He also published commemorative writings, such as a memoir of Niccolò Tommaseo (containing a number of letters by Tommaseo, whom he knew quite well), which he dedicated to Mauro Ricci, the Piarist teacher of Italian.

In a note that was partially autobiographical he also included a letter by Caverni regarding his Osservazioni on the commentary to the Divina Commedia edited by Tommaseo and on the astronomical notes of Giovanni Antonelli. In the following years Tommasi published memoirs of Filippo Cecchi and Mauro Ricci, the preface to two stories by Ivan Turgenev translated by Edoardo Zucchelli, but, above all, the editions of some contemporary correspondence, including letters of Giuseppe Giusti, Massimo d’Azeglio and Tommaso Grossi.

In 1875-76 he was director of “Il Giusti”, a Florentine periodical of science, letters and arts. He later moved to Rome to work for the “Gazzetta ufficiale”, first as editor, and then, from 1924, as chief archivist and subsequently (from 1925) as manager of the office dealing with legal publications within the Ministry of Justice and Ecclesiastical Affairs. In 1916 he delivered and printed the funeral oration for the Director General, Giovanni Battista Ballesio. In the same year he published in facsimile some letters of Pietro Fanfani, Enrico Bindi e Cesare Guasti, which he had received when he was young in response to sending them his early publications.