Benchmarking Gaia DR3 Apsis with the Hyades and Pleiades open clusters

The Gaia astrophysical parameters inference system (Apsis) provides astrophysical parameter estimates for several to 100s of millions of stars. We aim to benchmark Gaia DR3 Apsis. We have compiled about 1500 bona fide single stars in the Hyades and Pleiades open clusters for validation of PARSEC isochrones, and for comparison with Apsis estimates. PARSEC stellar isochrones in the Gaia photometric system enable us to assign average ages and metallicities to the clusters, and mass, effective temperature, luminosity, and surface gravity to the individual stars. Apsis does not recover the single-age, single-metallicity characteristic of the cluster populations. Ages assigned to cluster members seemingly follow the input template for Galactic populations, with earlier-type stars systematically being assigned younger ages than later-type stars. Cluster metallicities are underestimated by 0.1 to 0.2 dex. Effective temperature estimates are in general reliable. Surface gravity estimates reveal strong systematics for specific ranges of Gaia BP-RP colours. We caution that Gaia DR3 Apsis estimates can be subject to significant systematics. Some of the Apsis estimates, like metallicity, might only be meaningful for statistical studies of the time-averaged Galactic stellar population, but are not recommended to be used for individual stars.