Mo. Rev. Stat. § 509.020: Caption of pleading — what set forth.

Every pleading shall contain a caption setting forth the name of the court, the title of the action, the file number, and a designation as in section 509.010. In the petition the title of the action shall include the names of all the parties, but in other pleadings it is sufficient to state the name of the first party on each side with an appropriate indication of other parties.