Magic will ask for your confirmation before making a purchase
If Magic is offering to make a purchase for you, it will wait for your written confirmation to proceed. There’s no special way to confirm. Yes, yep, OK, K, Y, and confirm all work.
If you’d like Magic to go ahead and make the purchase without waiting for your confirmation, say “autoconfirm” while making a request. You can also say a specific price you’d be willing to autoconfirm. For example: “autoconfirm anything under $200.” This is especially helpful if you need something urgently or you know you’re not going to be able to respond to Magic reliably.