CanFulfillIntentRequest on Alexa (still in beta) allows users to access your skill without needing enable and invoke it with the invocation phrase.
By default, a handler will return "NO" to every CanFulfillIntentRequest. You need enable it specifically for each handler.
To enable, add the key of accessibleThroughDiscovery with value true to the handlers data field.
Note: You must have a default global fallback enabled for it to work. Alexa will test all the intents in your interaction model, which most likely don't have handlers associated with them. They will then automatically redirect to the default global fallback, which will return "NO" as a response to the request.