This proposal, discussed as the Micropub 2026 popup(https://indieweb.org/2026/Micropub), would be to write into the spec requirements for any new properties and commands added to the spec or in the form of an extension.

It would require that they either have a defined vocabulary set in the spec or in the extension that MUST be supported, or have a method of querying to determine supported vocabulary.

A possible place to add this would be in 3.3.5, the section on unrecognized properties. Of course, there may be a case to relocate that section outside of create at the same time, being as it technically applies to other areas.