  With an increased focus on the observing and modelling of mini-Neptunes,
there comes a need to better understand the tools we use to model their
atmospheres. In this paper, we present the protocol for the CAMEMBERT
(Comparing Atmospheric Models of Extrasolar Mini-neptunes Building and
Envisioning Retrievals and Transits) project, an intercomparison of general
circulation models (GCMs) used by the exoplanetary science community to
simulate the atmospheres of mini-Neptunes. We focus on two targets well studied
both observationally and theoretically with planned JWST Cycle 1 observations:
the warm GJ~1214b and the cooler K2-18b. For each target, we consider a
temperature-forced case, a clear sky dual-grey radiative transfer case, and a
clear sky multi band radiative transfer case, covering a range of complexities
and configurations where we know differences exist between GCMs in the
literature. This paper presents all the details necessary to participate in the
intercomparison, with the intention of presenting the results in future papers.
Currently, there are eight GCMs participating (ExoCAM, Exo-FMS, FMS PCM,
Generic PCM, MITgcm, RM-GCM, THOR, and the UM), and membership in the project
remains open. Those interested in participating are invited to contact the
authors.
