Full Idea
Grice's maxim of quantity says 'make your contributions as informative as required'.
Gist of Idea
Grice's maxim of quantity says be sufficiently informative
Source
report of H. Paul Grice (Some Models for Implicature [1967]) by Ofra Magidor - Category Mistakes 5.2
Book Reference
Magidor,Ofra: 'Category Mistakes' [OUP 2013], p.112
A Reaction
Is the 'requirement' of informative for the speaker or for the listener? It is easy to image situations where, one way or the other, the two people don't agree about informativenss.