Monk wanted midfield cover with Leon Britton ruled out for a month by knee trouble but he said England Under-21 international Carroll had been on Swansea's radar for some time.
"He's a very good footballer who will very much suit us," Monk said.
"We've watched him, done our analysis over the years, seen him at Spurs and a lot of him at QPR.
"I've spoken to a lot of people who have trained with him and coached him and they speak very highly of him
"He can show that good side of football we need because he's good with the ball.
"He can pass and move and get himself in good positions and I think he'll offer us another option."
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