---
type: InsightHub
name: Protocols and agent checkout
id: "https://selfe.ai/insights/protocols-and-agent-checkout"
url: "https://selfe.ai/insights/protocols-and-agent-checkout"
publisher: "did:web:selfe.ai"
description: "The real plumbing under agentic commerce: protocols, credentials and payment."
---

# Where the request meets the road.

> How a purchase completes.

What has to happen, protocol by protocol, before an agent's decision becomes your transaction.

## Start here

- [The plumbing behind every agent purchase.](https://selfe.ai/insights/protocols-and-agent-checkout/the-plumbing-behind-every-agent-purchase) — Every purchase an AI agent completes, whatever it's buying, passes through the same four jobs: proving who the agent is, proving what it's allowed to spend, connecting to the business's own systems, and completing a transaction the business can settle. The protocols in this hub each do one of those jobs. None of them does all four.

## More in this hub

- [What a checkout API call looks like from the other side.](https://selfe.ai/insights/protocols-and-agent-checkout/what-a-checkout-api-call-looks-like-from-the-other-side) — Strip away the protocol names and an AI agent completing a purchase is, from a business's own system, just another API request arriving with a specific, checkable shape. Here's roughly what lands, and what a business's system has to do with it.
- [UCP and the checkout handoff: what changes when a purchase completes inside the conversation.](https://selfe.ai/insights/protocols-and-agent-checkout/ucp-and-the-checkout-handoff-what-changes-when-a-purchase-completes-inside-the-c) — Every other protocol in this hub gets a purchase ready. UCP is the one that completes it: the point where a business hands back a confirmed order without sending the customer off to finish the job on a website.
- [MCP, explained: what it actually connects, and what it doesn't.](https://selfe.ai/insights/protocols-and-agent-checkout/mcp-explained-what-it-actually-connects-and-what-it-doesnt) — Model Context Protocol gives an AI agent a standard way to call into a business's own systems: read live data, run a search, trigger a defined action. It has nothing to do with payment or identity. That's a separate job, done by separate protocols.
- [Holds, mandates and spend limits: how a business keeps control of an automated payment.](https://selfe.ai/insights/protocols-and-agent-checkout/holds-mandates-and-spend-limits-how-a-business-keeps-control-of-an-automated-pay) — A mandate only says what an AI agent was allowed to try. What protects a business is what happens on its own side of the transaction: the hold it places, the ceiling it enforces, and the mandate scope it insists on before a booking or order is allowed to proceed.
- [AP2 and agent payments: how an agent proves it's allowed to spend on someone's behalf.](https://selfe.ai/insights/protocols-and-agent-checkout/ap2-and-agent-payments-how-an-agent-proves-its-allowed-to-spend-on-someones-beha) — A credential proves an AI agent is who it says it is. AP2 (Agent Payments Protocol) proves something narrower and more specific: that a real person authorised this exact spend, up to this exact limit, and a business can verify that before it charges anything.
- [Agent credentials: the token that says "yes, actually let this agent buy."](https://selfe.ai/insights/protocols-and-agent-checkout/agent-credentials-the-token-that-says-yes-actually-let-this-agent-buy) — Before an AI agent can act on anyone's behalf, something has to vouch for it. An agent credential is the short-lived, scoped proof a business checks before it trusts a request enough to act on it.
- [A2A, explained: how one agent proves what it's asking another to do.](https://selfe.ai/insights/protocols-and-agent-checkout/a2a-explained-how-one-agent-proves-what-its-asking-another-to-do) — A shopping AI agent rarely finishes the whole job itself. It hands specific tasks to other, more specialised agents along the way. Agent2Agent protocol is how one agent describes a task to another clearly enough that the second agent can trust it and act on it.

## Act on this

- [Check whether an agent can buy from you](https://selfe.ai/agentic-commerce/buyability-check) — the free readiness scan.
- [Discover venues](https://selfe.ai/api/registry/discover) — `POST`, semantic browse across the registry.
- [Match a bookable answer](https://selfe.ai/api/registry/match) — `POST` with dates and party size.
- [Verify Selfe's identity](https://selfe.ai/.well-known/did.json) — `did:web:selfe.ai`.
- [Agent card](https://selfe.ai/.well-known/agent-card.json) — how to connect over A2A or MCP.