I would argue that it's not authoritative. Nothing guarantees that the records in the db match that schema; the closest you get to a guarantee is your diligence to 1) run a job mutating all records every time you change your in-code schema and 2) ensure that nothing but your latest application code can write to the db.

OTOH, `\d users` in PostgreSQL is authoritative; there cannot be a row that does not conform to the fields, types, and constraints listed there.