  We study the nature of the recently observed $P_{cs}(4459)$ by the LHCb
collaboration by employing three methods based on the elastic effective-range
expansion and the resulting size of the effective-range, the saturation of the
compositeness relation and width of the resonance, and a direct fit to data
involving the channels $J/\psi\Lambda$, $\Xi'_c\bar{D}$ and $\Xi_c\bar{D}^*$.
We have also considered the addition of a CDD pole but this scenario can be
discarded. Our different analyses clearly indicate the molecular nature of the
$P_{cs}(4459)$ with a clear $\Xi_c\bar{D}^*$ dominant component. In relation
with heavy-quark-spin symmetry our results also favor the actual existence of
two resonances with $J=1/2$ (the lighter one) and $3/2$ (the heavier one) in
the energy region of the $P_{cs}(4459)$. In the scenario of two-resonance for
the $P_{cs}(4459)$, the inclusion of the $\Xi_c'\bar{D}$ channel is required
for the their mass splitting and it allows one to determine the spin structures
of the two resonances.
