Mo. Rev. Stat. § 429.180: Pleadings as in other civil cases.

The pleadings, practice, process and other proceedings in cases arising under sections 429.010 to 429.340 shall be the same as in ordinary civil actions and proceedings in circuit courts, except as herein otherwise provided. The petition, among other things, shall allege the facts necessary for securing a lien under said sections, and shall contain a description of the property charged therewith.