The Alexa Skills Kit API relies heavily on an “intents + slots” system where you request specific nouns/verbs from the user such as a first nam or a date and the webhook only sees that specific information. This makes it difficult to wire up third party NLP systems, although there are hacks out there[0].
[0] https://blog.init.ai/alexa-can-you-add-custom-nlp-to-amazon-...