Simple boundary conditions that can represent the flow emanating from zero-net massflux (ZNMF) jets in grazing flows are examined. Two-dimensional Navier-Stokes simulations of ZNMF jets in grazing flow are used to determine the key characteristics of the jet profile, and these are used to construct a series of boundary condition models. These boundary condition models are then tested for a jet emanating into an attached boundary layer as well as a boundary layer with an induced separation bubble. A key finding of the current study is that simple plug-flow type models of ZNMF jets can lead to incorrect trends in separation control. Based on this analysis, we select two models that are simple, yet provide a reasonable representation of the ZNMF jet in a grazing flow. An empirical closure of these models is also suggested.