In some class of BSM models, such as SUSY, DM may be searched for using high pT jets + missing ET, where DM (X) may be produced from the decay of a heavy particle H. If mH is close to mX, the signature is ISR , and may be monojet like, and there is much information on the nature of H and X. I will discuss how the leading jet distribution contains information on both mH, color representation and spin of the particles, but to extract the information fully, one needs to predict the distribution with less than 10% accuracy for the parameter region that may be studied at HL-or HE-LHC. Then I turn into the theoretical error in the current best NLO MC based on MC@NLO scheme, such as MG5 and Sherpa, and discuss if such accuracy can be achieved.