This API can describe most Wikidata items automatically. For some item types (e.g. biographies) in some languages, long descriptions are available. Blog entry, code repo, translations.
Q Language
Mode short long description (where possible)
Links plain text HTML/Wikidata HTML/Wikipedia Wikitext/Wikipedia HTML/Reasonator
Redlinks Plain text AutoDesc Reasonator For HTML/Wikipedia links with no corresponding Wikipedia page; long desc only
Format JSON (takes &callback) Pretty JSON HTML page
Infobox Yes No (for wikitext output only)
Examples: