Prompt design basically defines the character of the AI system. If we take movie making as an analogy, Prompt desiging is like a director of a movie who defines the characters of the actors as per the story. Without proper definition of a character the role of that actor would be flat and look out of place .The character will not display appropriate emotions, dialogue delivery, subtle changes in body language etc., for different scenes, ultimately resulting in the failure of the movie due to a big disconnect between the audience and the characters.
Hence the quality of a prompt design will directly impact the quality of the output of AI.
When we consider a conversational BOT, though it can understand Natural language and process it, how it responds as per the defined role will play a major role in the AI's usability and experience that user gains.
Let's say for example a 10 year old is eager to know the Theory of relativity. If the AI responds too technically that not even a single word makes sense to that 10 year old, then in the eyes of the 10 year old AI is not of any help to him. Instead, if the prompt design had included to check the age of the requestor or use appropriate analogy to explain concepts as per age of the requestor, then it would have been more useful.
Another example, say a shop floor manufacturing supervisor who enters the production data into the ERP systems, finds few keys on his key pad non functional. So he chats with company's IT support BOT and types " some keys not working in the keyboard", the BOT responds by asking what is the OS version, what is the system Tag, when was the last software patch done etc..The user just shuts the BOT, picks up the phone and talk directly to IT support personnel..The very purpose of the IT support chat BOT failed.
Here, the BOT should know that it is interacting with a non technical employee and has to converse in his language, ask information which he is capable of giving. There is a famous quote in Marketing, 'always talk the language of the customer ".
When computers were boom in the business world, it started with personal computer, slowly it evolved to personalized computing. The same way AI is just entering to business world, there is no perfect system, but there must be a robust process put in place to monitor, gather feedback and improve the systems, in case of conversational BOTs , improve the prompt.
Again back to movie analogy, the result of a movie be it success or failure depends on how well the audience recieve the product. Successful or not, by having a feedback mechanism it helps the director to learn and make improvements in his next movie. Again it is a cycle of iterations that is applicable in every aspects of life. The same is applicable to AI system as well. Like how a director cannot ask an aged character to dance difficult steps in a movie, the prompts too must be specific, formatted, be on the context and talk the language of the user.
In my view, the generalised AI will slowly be evolved into personalized AI in the coming years. The AI will develop capabilities to understand about the different users and serve them as per their personalized requirement.
In summary, The prompt design (continuously evolving and improving) will make the AI descisions more relevant, useful and will serve the purpose for which it was designed.