As part of the Space-based multi-band Variable Objects Monitor mission, the Microchannel X-ray Telescope observes the soft X-ray band of the gamma-ray burst afterglows. The so-called lobster-eye optics focus X-rays to the camera subsystem that performs imaging and spectroscopy of a region of the sky 58 × 58 arcmin2 wide centered on the burst detected by the ECLAIRs instrument. The recorded photo positions are used by the onboard scientific software to rapidly localize the source, whereas spectral information is used on ground to model the properties of the gamma-ray bursts. The first months in orbit were intensively used to tune the parameter settings of the detector and the calibration method to provide high availability of the camera and accurate spectroscopy to the users. The paper presents the design of the camera validated by on-ground testing, the tuning phase in flight and the performance of the camera at the beginning of the mission. Perspectives are given concerning the evolution of the spectral response during the mission.