Unlike mage knights and mage techs, a mage smith is a mage who spends their item with the creation and manipulation of artifacts. There are considerably fewer smiths than the other types, mainly because it is a dangerous task due to the explosive nature of feedback.
Smiths are also mages who are involved in the construction trades such as bricklaying, plumbing, and carpentry since most involve manipulating the material in addition to strengthening or changing its characteristics. There is some overlap with techs in this regard.
Finally, smiths are also the ones useto change the resonance of an artifact to make it safer to use within populated areas. This is required to avoid charges. However, changing resonance is also a time-consuming task that requires months or even years of isolation and carefully controlled environments.