The apartment is perfectly located for a convenient stay in Florence. As instructed we called once we arrived at the station and we were met at the apartment by a lady who works for Federico. It seems like he/his company has a number of apartments and she checks people in. We never spoke directly with Federico.
We were given a quick overview of the apartment and were able to drop our bags there despite being earlier than regular check in (before 1pm), and the apartment was still being cleaned from the previous guests.
The apartment is a bit smaller than it appeared on the photos but perfectly fine and a convenient base for exploring Florence.