We present FinnTreeBank 3, a treebank and parsebank for Finnish, and focus on its design and development. First, we describe our method of specifying the core linguistic representation with descriptive grammars (rather than with text corpus samples) and conclude with a reference to empirical experiments on the specifiability of Finnish dependency syntax. We outline the linguistic representation used in describing Finnish morphology and syntax. We describe one use of a systematically specified linguistic representation and “grammar definition corpus”: as a task specification for a subcontractor to create a parser engine and a parsebank for the language resource service.