The 33-year-old, who has started six games for the Scottish outfit this season, joined County from Inverness Caledonian Thistle in 2011.
Munro told Moray Firth Radio: "When you turn 30, your mind looks to the end of your career and the next stage. We have another kid on the way as well, to make it three, so that enhances it.
"I asked the manager if my time was up and we both came to the agreement. He didn't want to stand in my way if that's how I felt, so credit to the manager and (director of football) George [Adams] for getting things done so quickly.
"Everyone knows when it's time for change. I wasn't going to play as much as I wanted to. I need to go into the world now and the next part of my career. I wasn't going to go beyond the summer anyway so it gives me a few months' head start to go into a new career."
Munro started his professional career in 1998.