Add the chicken breasts, wild rice, chicken broth, cream of chicken soup, carrots, celery, onion, garlic powder, parsley, salt, and pepper to the slow cooker.
Stir everything together until the soup and broth are evenly combined.
Cover and cook on low for 6 to 7 hours, until the chicken is cooked through and the rice is tender.
Remove the chicken breasts from the slow cooker, shred them with two forks, and return the shredded meat to the pot.
Stir in the half-and-half until the broth turns creamy and smooth.