Ruaridh is one of two uncapped players selected for the squad preparing for the February 8 Six Nations opener against Wales.
Ruaridh signed as a pro with Glasgow in May and has started just one professional game, but he made it count with an impressive display in last month's Heineken Cup defeat at Bath.
"I got a phonecall last night so it's quite a nice surprise," Ruaridh told Sporting Life.
"I've had a few texts but I've been out doing some fitness work today so that's been my celebration!"
Ruaridh, who spent the first six months of his life in Northampton, is widely regarded as one of the brightest prospects in Scottish rugby.
He said: "Ever since I started playing rugby when I was young, I watched the internationals. You just dream of playing them and playing at Murrayfield.
"Hopefully, the dream is starting to come true."
Upon announcing his squad today, head coach Frank Hadden was fulsome in his praise of the youngster.
Ruaridh said: "It's obviously good to hear coming from the head man himself. It gives you confidence that you're doing something right if he's saying it."
However, Hadden did express some concern at the youngster's lack of senior experience at fly-half.
The player himself said: "I've been fly-half pretty much all my life and I've had a few games at full-back.
"I've played a mixture of both this year but stand-off is where I'm most comfortable."
He added: "Obviously, there's going to be pressure there and being involved with Scotland is the biggest experience I'll have had.
"But, as a professional, that's what you relish. You want to be in the big-pressure situations - that's hopefully where you can excel."
And Ruaridh was not shy about declaring his ambition to challenge club-mate Dan Parks and Edinburgh's Phil Godman for the number 10 jersey.
He said: "As a player, whatever squad you're in, you want to be playing. I'm definitely down the pecking order at the moment behind Godman and Parks etc. They'll be pretty hard to get past.
"I'm just looking to stake a claim in training, whether I make the first game or not.
"Hopefully with the 'A' games, if I get a chance there, I can prove myself.
"You never know what can happen. You can get injuries, but hopefully if I'm playing well, I can get involved."