  We perform spectral energy distribution (SED) fitting to 711 luminous X-ray
AGN at 0.7 < z < 4.5 using 10-bands of optical and infra-red photometric data
for objects within XMM-SERVS. This fitting provided 510 reliable (reduced $\chi
^2 < 3$) inferences on AGN and host galaxy properties. The AGN optical
(3000\r{A}) luminosity inferred from SED-fitting is found to correlate with the
measured X-ray (2-10 keV) luminosity, in good agreement with previous work.
Using X-ray hardness as a proxy for AGN obscuration, we also study the
differences in the host galaxy properties of obscured and unobscured AGN. Both
populations have consistent stellar masses (log$_{10}(M_*/M_{\odot})$ = 10.88
$\pm0.09M_\odot$ and log$_{10}(M_*/M_{\odot})$ = 10.8 $\pm0.1M_\odot$ for
unobscured and obscured AGN respectively). We also find evidence for varying
AGN emission line properties from a standard AGN template in 18.8% of the
sample with a reduced $\chi^2 < 3$ where the inclusion of an additional
emission line strength free parameter was found to improve the quality of the
fit. Comparison of these fits to SDSS spectra showed that emission line
properties inferred from broadband photometry were consistent with the results
from spectroscopy for 91% of objects. We find that the presence of weaker, more
blueshifted emission lines as inferred from the SED fits are associated with
more negative values of $\alpha_{ox}$. While the correlation between the
hardness of the ionising SED and the emission line properties has been known
for some time, we are able to derive this correlation purely from broadband
photometry.
