  We present a multi-frequency study of PKS J1222$+$0413 (4C$+$04.42),
currently the highest redshift $\gamma$-ray emitting narrow-line Seyfert 1
($\gamma$-NLS1). We assemble a broad spectral energy distribution (SED)
including previously unpublished datasets: X-ray data obtained with the NuSTAR
and Neil Gehrels Swift observatories; near-infrared, optical and UV
spectroscopy obtained with VLT X-shooter; and multiband radio data from the
Effelsberg telescope. These new observations are supplemented by archival data
from the literature. We apply physical models to the broadband SED,
parameterising the accretion flow and jet emission to investigate the disc-jet
connection. PKS J1222$+$0413 has a much greater black hole mass than most other
NLS1s, $M_\mathrm{BH}\approx2\times10^{8}$ M$_\odot$, similar to those found in
flat spectrum radio quasars (FSRQs). Therefore this source provides insight
into how the jets of $\gamma$-NLS1s relate to those of FSRQs.
