Also, some Specification constraints cannot be represented with the JSON Schema so it's highly recommended to employ other methods to ensure compliance.

Maybe one day, JSON Schema would be able to express all the constraints in the OpenAPI spec, but I suspect some are going to be really hard.

When we do release a final version of JSON Schema, please do not use JSON Schema to guarantee an OpenAPI document is valid. It cannot do that. There are numerous constraints in the written specification that cannot be expressed in JSON Schema.