Min number of terms in a log reg model

Master's student here working with data that lacks some basic socio-demographic characteristics on a population, but I am interested in one exposure of interest and two covariates to look at relationship with a categorical outcome. I am wondering if this is too few terms for a logistic regression model? Not sure what 'convention' is here, as I only hear about over-doing it with too many variables. Any advice/links on literature about this are greatly appreciated!