The head coach was asked about his young full back, who signed from Chelsea permanently in the summer.
Hall had spent last year on loan at the Magpies as part of a loan with a buy obligation deal.
As they take on Chelsea twice in the coming seven days, Howe told reporters: "When we were looking at this deal last year, it was the lack of equal players in that position. We took an opportunity to sign a young player that we knew would be growing and developing into the player that he was going to become.
"We wanted to grab that opportunity while we had it and we felt if we waited, it would possibly be beyond us. He took time to develop, as all young players do, but the growth in him towards the back end of last season and, certainly, this season has been really strong.
"He's adding layers all the time, with different strengths to his game, and I can only see that improving."