The following fields need to be added, and each of them should then be used in one use case:
[x] statement id - GetStatement - https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/955339
[x] property id filter - GetItemStatements - https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/955686
[] requested fields - GetItem - https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/955354
[x] language code - GetItemLabel - https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/955676
[x] property id - GetPropertyStatement - https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/955681
[] Statement + edit metadata (combo deal because no use case comes with only the edit metadata) - AddStatement - https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/955960
[] Patch - PatchItemLabels - https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Wikibase/+/956805
[] Label - SetItemLabel - https://gerrit.wikimedia.org/r/956907
[] Description - SetItemDescription