S,

No, the RESTBase mobileapps service[1] doesn't do this currently. That should be possible, though.
The service currently uses action=mobileview under the hood. This means it gets it first from the WP instances, and it that one doesn't have it it would go to Wikidata. 

In the future we'll likely switch to Parsoid for the backend requests but I don't know when that will happen. We then might have to request the description using something like action=query&prop=pageterms&wbptterms=description[1] if that's not included in Parsoid.

[1] https://www.mediawiki.org/wiki/Wikimedia_Apps/Team/RESTBase_services_for_apps
[2] https://en.wikipedia.org/wiki/Special:ApiSandbox#action=query&prop=pageterms&format=json&wbptterms=description&titles=Cat

Bernd

On Mon, Aug 17, 2015 at 4:56 PM, S Page <spage@wikimedia.org> wrote:
On Sat, Aug 15, 2015 at 5:08 AM, Magnus Manske <magnusmanske@googlemail.com> wrote:
Ah, but when auto-descriptions get better, how do we know which should be updated, and which have been "improved" bu humans? Because people will screem bloody murder if we replace "their" descriptions with automatic ones, even if those are better.

Would it be acceptable to *generate* a description on the fly if there isn't a description in the user's language, but never *replace* an existing description in Wikidata?

AIUI this is what RESTBase is good at: in response to API requests for information about a page, some backend generates information, RESTBase caches it for future requests but RESTBase doesn't update the content databases. If I'm right (unlikely :-) ), then the upcoming MobileApps service could do this without anyone screaming.

Maybe the MobileApps service already does this, I'm not sure what https://restbase.wikimedia.org/en.wikipedia.org/v1/page/mobile-text/Cat puts in the "description" field if Wikidata's description is empty.

figuring out which descriptions we can overwrite is next-to-impossible.

So don't try. The game becomes: present the generated description next to the manual Wikidata description, and if enough users prefer the former, blank out the Wikidata description.

Cheers,
--
=S Page  WMF Tech writer