Mo. Rev. Stat. § 376.1522

Each discount medical plan organization shall maintain a current list of the names and addresses of the providers with which it has contracted on a website page, the address of which shall be prominently displayed on all its advertisements, marketing materials, brochures, and discount cards. This section applies to those providers with whom the discount medical plan organization has contracted directly, as well as those who are members of a provider network with which the discount medical plan organization has contracted.