There are a few upcoming breaking changes in the Wikibase API.
* The items id as exposed to the outer world is now a numeric id. This
will be prefixed with a letter and this letter will be used internally
during lookup. Do not hardcode interpretation of this letter as it can
be configured, but once configured it will be type-specific for the
type of entity.
https://bugzilla.wikimedia.org/show_bug.cgi?id=40381
* The encapsulating "items"/"item" in the reply will be replaced by
"entities"/"entity" and it will be a new type-field in each entity.
This field will have an identifier that says which kind of entity is
in there.
https://bugzilla.wikimedia.org/show_bug.cgi?id=40407
https://bugzilla.wikimedia.org/show_bug.cgi?id=40408
John Erling Blad