Harper ended his lengthy association with Newcastle earlier in the summer and he has now accepted a deal with Premier League new boys Hull.
The 38-year-old has been added to Steve Bruce's squad to provide competition and cover for fellow new signing Allan McGregor at the KC Stadium.
"We just thought we needed a bit of experience," Bruce told Sky Sports News.
"We let a young kid, Mark Oxley, go to Oldham to get some experience, and we just needed a bit of experience.
"We got in Allan McGregor and now we've brought in Steve, who has been around the Premier League for 20 years.
"He'll be good in the dressing room and good for the younger players we have got in the squad. With his experience, he will certainly help me to try to achieve what we want to achieve.
"You can't beat a bit of experience and Steve has got that in abundance. We've seen him at the back-end of last season playing against Arsenal and he did very well in the game, so I had no problems bringing him in."
With a large chunk of Hull's squad having no Premier League experience to call upon, Bruce felt it was important to bring in a player of Harper's stature.
He continued: "We have added a couple of people who know what it's about.
"The vast majority of the squad have worked extremely hard to get in the Premier League over the last few years. I'm talking about Stephen Quinn, George Boyd, people like that, and some of the younger players - James Chester, for example, didn't quite make the grade at Man U.
"They're all desperate to try and prove themselves, and be, Premier League players, and that's the challenge ahead for them."