A human codebook is a structured reference guide that defines the specific categories, rules, and operational criteria used by human annotators to systematically label, classify, and interpret qualitative data. In empirical research and computational text analysis, it provides explicit definitions, boundary guidelines, and representative examples to ensure consistency and high inter-annotator reliability during manual coding. This standardized protocol establishes the ground-truth criteria necessary to produce reliable validation datasets, which are subsequently used to instruct human coders as well as train, prompt, and benchmark automated classification systems and large language models.