validate property

Whether a document is checked against the schema before it runs.

Off by default, so that taking this version changes nothing for a server already running: an unknown field or fragment keeps yielding an empty object and an undeclared variable keeps yielding null, as in 3.2.

Turn it on to get what the specification requires, which is that a document failing validation is refused rather than executed. Do it once you know what your clients send, because a client whose document the schema refuses stops working the moment you do.