Bridcutt has been a regular for promotion-chasing Brighton this season in the Championship, but he is a surprise inclusion and the Reading-born midfielder's call-up is subject to Scottish FA clearance.
The 23-year-old former Chelsea trainee qualifies for Scotland through his grandfather from Edinburgh.
Hull City forward Boyd recently joined the Tigers on loan from Peterborough, scoring twice on his home debut, and will be targeting his first full cap after representing Scotland B in 2009.
Mackay-Steven is one of the brightest talents in the SPL and the winger has scored fives goals for Dundee United, including the winner in the recent Tayside derby.
Manager Gordon Strachan admits he is keen to freshen up his squad with their qualification hopes all-but over.
"Gary Mackay-Steven has been terrific this season and I think it is only right that we recognise young Scottish talent," he told the SFA website. "Liam is a player I have known for a while and is highly regarded in the holding midfield position.
"Again, George is a player I have watched for years - I tried to sign him at Middlesbrough - and is in good form at Hull City."
Southampton left-back Danny Fox has been recalled, but there was
no place for Rangers' Lee Wallace or Phil Bardsley, who has not played for
Sunderland since 19 January.
Blackpool winger Matt Phillips and QPR forward Jamie Mackie both drop out and Celtic captain Scott Brown is absent with an abductor injury which could rule him out for the season.
In-form Hibernian striker Leigh Griffiths was not included but Birmingham's Chris Burke retains his place after returning to the fold for last month's 1-0 friendly win over Estonia.
Gary Caldwell will be captain in the absence of the injured Darren Fletcher as
Scotland face Wales at Hampden Park on 22 March before the away clash in Serbia on 26 March.
Scotland squad: Gilks (Blackpool), Marshall (Cardiff), McGregor (Besiktas); Berra (Wolves), Caldwell (Wigan), Fox (Southampton), Hanley (Blackburn), Hutton (Real Mallorca), Martin (Norwich), Mulgrew (Celtic), Webster (Hearts); Adam (Stoke), Bridcutt (Brighton), Burke (Birmingham), Commons (Celtic), Dorrans (West Brom), Forrest (Celtic), Mackay-Steven (Dundee United), McArthur (Wigan), Morrison (West Brom), Snodgrass (Norwich); Boyd (Hull), Fletcher (Sunderland), McCormack (Leeds), Maloney (Wigan), Miller (Vancouver Whitecaps), Naismith (Everton), Rhodes (Blackburn).