I am a professional chatbot developer having more than three years experience in the domain and I have deployed bots for large e-commerce and other organizations. An advanced assistant for your business cannot be made just by using NLP engines like dialogue flow, Watson assistant, chatfuel and many others out there it is the right mix of the use case (conversational flow) and cognitive services such as tone analyzing, text to speech, speech to text, knowledge studio(large documents querying), image recognition (for mostly e-commerce purpose), etc. I also have experiece in using bot frame works like microsoft bot framework and howdy botkit