User Story
As a client developer, I want a unified API for editing article title descriptions that abstracts away the complexity of the underlying description sources

Background
For every Wikipedia except English Wikipedia, the article description included in the page summary is from Wikidata. For English Wikipedia, as described in T256817, it now must come from the short description template in the article. It'd be ideal to have a single API for editing this title description that handles the underlying complexity of either editing Wikidata or English Wikipedia.

Rough Spec
No strong preference . The client should be able to make an authenticated request with the description text as a parameter and have the short description updated or created in the article itself.

Open questions
Should wikitext be supported?
Should it be a MediaWiki REST API, an action API, or something else?

Rough implementation plan
On enwiki, the API would edit the {{short description}} or {{SHORTDESC}} template in the article's wikitext. If the template doesn't exist in the wikitext, it should be added with the value provided.

On all other wikis, edit the Wikidata description for the entity associated with the article by using action=wbsetdescription.

The edits would be made as if the user who made the authenticated request had made the underlying edits directly.