Reliability of the selection function model, as estimated from a test sample comprising 2566 057 simulated galaxy clusters, none are used in the training phase. The x-axis represents the detection probability predicted by the selection function model. Top panel: y-axis representing the fraction of detected objects among all simulated objects in each bin. The shaded area corresponds to the 1σ binomial uncertainty. The dotted line represents the 1:1 relation. Bottom panel: histogram of clusters in the test sample per bin of predicted detection probability.