Two are written for the human setting the boundary, two for the agent spending inside it.
Connect an agent in four steps — sign in, create a Passport Key, copy the config, verify.
What an agent must do before and during a purchase. Read it before the first payment, not after a failure.
REST endpoints, Passport Key auth, limits and error codes.
The merchant-by-merchant field hints the bridge uses to fill a real checkout.
Every page here has a machine-readable rendering at the same address. curl -L z-zero.xyz returns the full guide; the index is /llms.txt and the A2A card is /.well-known/agent.json.