Outside of conditions preventing a severance. If the content of the get is lishmah, has eidim etc. When the husband or shaliach give it to her or place it in her daled Amos... Who cares or why would "I'm no longer your husband" disqualify the get? What is the source?
Avrahom Kevelson, United States
Dear Avraham,
By Kidushin, speech is part of the act of marrying her from the Torah.
By Get- Shulchan Aruch Even HaEzer 136:1,2,3 brings the Halachos of th speech said with giving the Get. See there the details and the Gemara sources brought in the Biur HaGra (including Kidushin 6)
The man is supposed to say that this is to divorce you. See there Beis Shmuel 136:1 hhich brings opinions if this is Min HaTorah or MidRabonon.
The reason seems to be to make sure its clear that he's giving the Get for divorce reasons. Therefore using the wrong speech will ruin the divorce on some level (Torah- d'Rabanan).
All the best, Reuven Weiner