What makes a song sound like Christmas
Christmas music has a sound palette that listeners recognise within two bars: sleigh bells on every beat, a tubular bell or chimes on the downbeat, a swinging brushed-drum feel borrowed from 1950s jazz, warm brass, a choir on the chorus, and lyrics that name the season directly. Ballads lean on piano and strings at 65 to 80 BPM; upbeat songs sit at 100 to 125 BPM with a shuffle or a swing. A key change into the last chorus is almost expected.
You do not need to describe all of that; the words Christmas, cozy and sleigh bells already pull the arrangement in the right direction. Spend your prompt instead on what only your song can have: the names, the traditions, the joke about the fairy lights that never work.