A descriptive grammar is a document that is intended to communicate important and complex patterns of knowledge within a speech community. Previous conceptions of linguistic grammars have emphasized a metaphor in which the internal grammar of a language is perceived as a “machine” that transforms thoughts into language structure. Written grammars were conceived as schematic representations of such machines. The present paper argues for a different metaphor. Because a grammar is primarily an act of communication, a good grammar possesses qualities known to hold of other communicative acts. The paper invokes recent work in linguistic pragmatics to help potential grammar writers conceptualize and present their work as an efficient and engaging act of communication.