From 2011-2015, Smith was tied for 27th in reliever fWAR with 4.0.
An extreme groundball pitcher (56.2%), his career FIP is 0.72 runs higher than his career ERA.
If you slot his RA9-WAR (8.3) into that leaderboard, he would have ranked 6th. If you look at the RA9-WAR leaderboard itself, he was 11th from 2011 to 2015.
Smith's career ERA is a cool 2.93. That's 65th out of 454 "qualified" relievers on Fangraphs since 2007, when he came into the league.
As a low velocity sinker/slider pitcher, Smith is not your typical setup reliever.
He was awful by FIP (4.99) in 2016 but decent by ERA (3.46).
His 88-90mph sinker didn't lose any velocity from 2014 and 2015, so there aren't any glaring signs of decline. His K and BB% were very close to his career rates. His GB% was a bit lower than normal, but still well above average.
His HR/FB rate was extreme compared to his career rate - probably just bad luck.
This signing is very good.
On this turf, with a strong defense, Smith is a great fit for Toronto.