  The neutral anomalies in $B$ decays are analysed in terms of the tree-level
exchange of an axion-like-particle (ALP), within the effective field theory
framework. The complete two-dimensional parameter space for ALP couplings to
electrons and muons is explored. The solutions to $R_K$ and to the two energy
bins of $R_{K^\ast}$ are confronted with the impact of ALP exchange on other
observables (meson oscillations, leptonic and semileptonic decays of $B$ mesons
including searches for new resonances, astrophysical constraints), as well as
with the theoretical domain of validity of the effective theory. Solutions
based on ALPs heavier than $B$ mesons, or lighter than twice the muon mass, are
shown to be excluded. In contrast, the exchange of on-shell ALPs provides
solutions to $R_K$ and/or $R_{K^\ast}$ within $2\sigma$ sensitivity which are
technically compatible with those constraints. Furthermore, a ''golden ALP
mass'' is identified at the frontier between the two energy bin windows of
$R_{K^\ast}$, which could simultaneously explain these two $R_{K^\ast}$
anomalies together with $R_K$; this calls for the convenience of different
energy binning which would easily clear up this (unlikely) possibility. The
impact of smearing on data analysis is also discussed. When loop effects are
taken into account, the solutions found can be in addition compatible with the
data on the $g-2$ of the electron but not simultaneously with those on the
$g-2$ of the muon. Furthermore, loop effects may require fine-tunings of some
coupling values.
