Generic nouns such as Sache and Ding pose a challenge for semantic annotation due to their referential underspecification and context-dependent meaning. Although frequently classified under categories like {artefact} or {object}, their actual referents often belong to abstract or cognitive domains, as in Der Placeboeffekt ist eines der faszinierendsten Dinge in der Welt der Medizin. Drawing on valency grammar, this study shows that these nouns activate different argument structures depending on their syntagmatic environment, reflecting semantic flexibility and combinatorial variability. Lexical databases such as GalNet or GermaNet frequently assign multiple synsets to these nouns, illustrating their ontological ambiguity. This paper examines whether large language models (LLMs) can replicate this nuanced classification. Using a gold standard corpus annotated by linguists, we implement a two-step prompting strategy —supplying LLMs with predefined semantic tags and contextual windows— to test their performance. The results underscore the limitations of current LLMs in dealing with the lexical underspecification of generic nouns, even when provided with an extended context window. These findings contribute to ongoing discussions on the automation of semantic tagging and point to meaningful ways in which AI systems can complement human expertise in natural language processing tasks.