The Root Of TrustGoogle's AP2 Explained
This is the third piece. By now the first two checks have answered two questions. Visa's Trusted Agent Protocol proved the agent is real. Mastercard's Agent Pay capped what it is allowed to spend. There is one question left, and it is the one that protects you from the purchase itself going wrong. Did you actually agree to this exact order.
That is what Google's Agent Payments Protocol, usually just called AP2, is built to settle.
Here is the problem it solves. An agent can be real and stay inside its spending limit and still buy the wrong thing. Maybe it picks the pricier item. Maybe the price changes between when you approved it and when it pays. Maybe the items in the basket quietly shift. You want a way to pin down the exact thing you said yes to, so nobody can change it after the fact.
AP2 does that by capturing your consent as a signed record. When you approve a purchase, that approval is turned into a small sealed document that says this exact cart, at this exact price, was approved by this person. That record travels with the order. When it reaches the store, the store can check it and see that the basket and the price trace straight back to your approval. If anything was swapped or nudged, it no longer matches, and the purchase does not hold up.
Think of it like a receipt you sign before the order goes through instead of after. Once your signature is on that exact order, the store cannot add an item or bump the price, because the thing you signed would no longer match what they are trying to charge.
One more thing worth knowing. AP2 is an open protocol. Google built it, but it is meant to work across different agents and providers, not just Google's own. That matters, because nobody wants a different rule for every shopping assistant.
And naturally, here is what AP2 does not do. It does not prove the agent is real, and it does not set the spending limit. It locks down the one specific purchase.
So put the three together and they are not rivals. They are layers. Visa settles who the agent is. Mastercard settles what it is allowed to spend. Google settles what exactly you agreed to buy. Three signatures, three different facts, all checked before a single dollar moves. That is how you put a fast, improvising AI agent inside a payment system that has always run on certainty, and still sleep at night.