The 'yamlet' package implements a file-based mechanism for documenting datasets. It reads and writes YAML-formatted metadata and applies it as data item attributes. Data and metadata are stored independently but can be coordinated by using similar file paths with different extensions. The 'yamlet' dialect is valid 'YAML', but some conventions are chosen to improve readability. Defaults and conventions can be over-ridden by the user. See ?yamlet and ?decorate.data.frame. See ?read_yamlet ?write_yamlet, and ?io_csv.