On MongoDB 3.4.4 I\'ve created a collection with a validator, but now some inserts fail this rules and I can\'t understand why.
You can see the validation rules (among other collection information) with db.getCollectionInfos() for all collections or db.getCollectionInfos({name: "myCollection"}) for a specific collection: MongoDB docs
db.getCollectionInfos()
db.getCollectionInfos({name: "myCollection"})
Have a look at this answer.