He was the chief of the embassy.

He went with confidence, flattering himself that he should find the Venetians more tractable and disposed to peace, both from their fear of John Visconti, and from some checks which their fleet had experienced, since their victory off Sardinia.

But he was unpleasantly astonished to find the Venetians more exasperated than humbled by their recent losses, and by the union of the Lord of Milan with the Genoese.
All his eloquence could not bring them to accept the proposals he had to offer.

Petrarch completely failed in his negotiation, and, after passing a month at Venice, he returned to Milan full of chagrin.
Two circumstances seem to have contributed to render the Venetians intractable.

The princes with whom they were leagued had taken into their pay the mercenary troops of Count Lando, which composed a very formidable force; and further, the Emperor promised to appear very soon in Italy at the head of an army.
Some months afterwards, Petrarch wrote to the Doge of Venice, saying, that he saw with grief that the hearts of the Venetians were shut against wise counsels, and he then praises John Visconti as a lover of peace and humanity.
After a considerable interval, Andrea Dandolo answered our poet's letter, and was very sarcastic upon him for his eulogy on John Visconti.
At this moment, Visconti was arming the Genoese fleet, the command of which he gave to Paganino Doria, the admiral who had beaten the Venetians in the Propontis.