Theoretical mass-radius diagram for a synthetic population of planets at 2 Gyr around an M dwarf with $M_{★}=0.4{\mathrm{M}}_{\odot }$, orbiting with periods P<100 d (Venturini et al. 2024). Each point represents a synthetic planet, and it is colour-coded according to its water mass fraction, with brown colours indicating purely rocky cores, and blue colours showing planets with a substantial amount of water (up to 50%), as predicted from formation beyond the ice line (Alibert et al. 2013; Raymond et al. 2018; Bitsch et al. 2018; Brügger et al. 2020; Izidoro et al. 2021; Venturini et al. 2020). TOI-771 b is marked with an orange diamond, and it is consistent with the rocky population.