We introduce the task of word and phrase-level polarity annotation for German as part of an attempt to develop a compositional theory of clause-level polarity determination. Thus, annotations should give access to the nested building blocks, the structural strata of polarity composition. Therefore and in contrast to existing polarity-tagged corpora, we annotate not exclusively on the basis of surface strings, but argue that proper polarity annotation of complex phrases requires access to their syntactic structures. We discuss the principles of our treebank design, and present the inter-annotator agreement of our kick-off annotations on a test suite of 270 sentences that was compiled specifically to contain interesting polarity combinations.