The case of a noun or pronoun is an inflectional form that indicates its grammatical function in a phrase, clause, or sentence
This tag should be used for questions about the German cases (nominative, accusative, dative, and genitive).
This tag is appropriate for questions targeting the inflection of a word, like declination of nouns.
Combine this tag with grammaticality if you are interested in whether or not your example sentence is a valid German sentence. Use grammar instead if you want to know, for example, rules to figure out which case is appropriate and how to inflect words.