Error ellipses of cosmological parameter estimation from the angular power spectra for the case of AGNs (σ₀ = 0.03, f_fail = 0.1) with priors. Blue dashed ellipses are the result of the Fisher forecast, whilst the shaded regions show the result of MCMC sampling done in COBAYA. Darker areas correspond to the 68% probability contour, and the lighter areas to 95%. On the diagonal of the plot grid, the marginalised histograms of the corresponding parameter are shown. The Fisher formalism provides a forecast in good agreement with the MCMC results.