6 months is definitely not too late! As the others said, it's actually better to wait until the dog is about a year or older before starting serious obstacle work, as agility is physically stressful on the body.
In the meantime you can work on plenty of foundation, tricks, obedience, play, etc. If you have a dog that focuses well and knows how to learn, agility is very easy to teach. There are tons of foundation things you can do while your dog is young that will make the "real" agility training very easy! (and as you progress, you'll discover that the foundation training is the real training)
Things that puppies can work on include clicker training and shaping, tricks (hand touch, walk backwards, spin left and right, retrieving, go around a cone, much much more!), impulse control, playing with toys (desire to play, tug, drop, and retrieve), body awareness (walking through cavalettis and ladders, walking and turning on a plank, perch work), noise and movement games (wobble boards, tippy planks, bang game, knocking things over, skateboards), more!
Find a good trainer with competition experience to help you get started. If you need help, you can give us your general location and we might know somebody to recommend.
Ryker: (USDAA) SR (DOCNA) C-BTA C-ISLA
Chandra: puppy in training!
Living forever in my heart, Solstice: (AKC) MX MXJ MJB (USDAA) PDCH (DOCNA) MEX-Bronze