The shell is described on the menu as a "marinated all-white meat chicken shell."
According to Foodbeast, the chicken shell is filled with lettuce, tomato, shredded cheese, and an avocado ranch sauce. Basically, it's filled the same as a typical Taco Supreme but with the avocado ranch sauce rather than sour cream and without any additional meat beyond the shell (a missed opportunity in my book).
The idea isn't so far-fetched seeing as sister brand KFC has already done the meat-as-bun thing with the Double Down and even used fried chicken as a hot dog bun abroad.
The price tag on the Naked Crispy Chicken Taco ranges from $2.49 to $2.99 each and it has been spotted in both Lost Hills, CA and Bakersfield, CA (a known testing ground for new Taco Bell menu items).
Photo by Cheez4444 / Imgur.