CONFORMANCE ≠ RELIABILITY

Your UCP checkout passes conformance. Does it actually work?

Independent, open, two-sided — and honest about its evidence: every check is proven to catch the bug it’s for, the suite is graded against two reference servers we didn’t author plus the official schema oracle, and we publish exactly what vouches for each check — including the ones only our own fixtures back so far.

Check your store → Test your agent →
276
Checked requirements (v2026-04-08)
48
Kill-tested against independent servers
0
False greens

Every normative MUST across three spec versions is accounted for — a proven check, a documented exemption, or a tracked gap. And the checks themselves are classed by proof: 48 live-wire (kill-tested against an independently-authored server — 17%), 73 graded by the official ucp-schema oracle (26%), 4 crypto self-tests, and 151 (55%) backed so far only by our own fixtures — a split we publish because you should know it before you trust a green. See the live coverage ↓

The problem
Conformance checks shape. Reliability is behavior.

A conformance pass means your JSON matches the schema and your endpoints answer. It doesn't say whether the right amount gets charged, whether the order really completes, or whether a forged response gets rejected.

Those are behaviors, and a checkout can be green on shape while it fails a real buyer at the moment of payment. So spck tests behavior on both sides: the merchant platform that sells, and the shopping agent that buys.

Which side are you building?
A UCP checkout takes two systems. We test both.
The sell side
Merchant platforms

You expose a UCP agentic interface over your catalog, cart, payments & checkout orchestration. We verify AI shopping agents can actually discover and buy from you — 227 checks, from the browser or your CI.

Check your store →
The buy side
Shopping agents

You build a shopping-orchestration AI that carts and checks out across merchant platforms over UCP. We catch the wrong-amount, phishing, and failed-checkout bugs conformance misses — before they cost a real user real money.

Test your agent →
Proof
Why you can trust a pass
A checker that can't catch bugs is worse than none. So every check is kill-rate tested — we inject the exact defect it should catch, and if it still passes, it's blocked from release. Checks cite a verbatim spec clause, and the whole suite self-validates in CI and goes red if any check loses its ability to catch defects. So when it flags a deviation, it is real and spec-cited — something you can act on, not noise. And a pass tells you how it was earned: every check carries a published evidence class — live-wire (kill-tested against a server we didn’t author), official-oracle, crypto self-test, or self-referenced (only our own fixture vouches for it) — derived mechanically from how the check runs and drift-gated in CI, so the split you read always matches a fresh derivation.
Transparency
Live spec coverage

Every normative MUST in each pinned spec version, accounted as a kill-rate-validated check, a documented exemption, or an open gap — regenerated with every change and enforced by CI (stale data or a coverage regression fails the build). The checked segment is further classed by evidence — each version's split renders below.

View the full matrix → Roadmap to 100%
See it live
Watch a checkout break — safely

The sandbox replays a shopping agent buying from a store that misbehaves on purpose — wrong totals, phishing links, forged confirmations — and shows the check that catches each one.

Watch the sandbox →
About
What is UCP?

The Universal Commerce Protocol (UCP) is an open standard for agentic and headless commerce. It enables AI agents, publishers, and any digital surface to discover products, create checkout sessions, and complete purchases through a unified API.

UCP defines a standard discovery profile, catalog search, checkout lifecycle (create, update, complete, cancel), fulfillment handling, payment processing, and order management.

Any commerce platform can implement UCP to make their merchants' products purchasable from anywhere — LLMs, publishers, shoppable media, and more.

The UCP protocol is maintained by Google's UCP team at ucp.dev. spck.dev is an independent, unofficial project — not affiliated with, endorsed by, or a substitute for the official UCP conformance suite; the official suite is authoritative.
📖
UCP Specification
ucp.dev — Official protocol documentation
🌐
REST API Binding
Checkout REST endpoint reference
Spec Repository
GitHub — Schemas, changelog, releases
✅
Official Conformance Suite
Google's Python test suite (targets v2026-01-23)