# The Launch Check

_a real paid purchase against your endpoint, signed, before you announce it_


X402 launch check: one real purchase attempt, signed stage by stage.

## At a glance

- **Attests:** The whole walk: the endpoint named, the moment, the exact User-Agent sent, every stage (approach, challenge, terms, screen, payment, settle, delivery) with its detail, the quoted amount after a 2xx, payment_attempt evidence, the seller-named transaction where one came back, the paying field wallet, and the record's evidence hash. The purchase certificate binds the same evidence hash in its attests field.
- **Input:** url (query parameters; input schema and checkout: https://scvd.store/menu/launch_check?view=compact)
- **Output:** A signed JSON walk record — verdict (settled, payment_refused, no_payment_gate, malformed_challenge, unpaid_by_rule or unreachable), every stage with its detail (approach, challenge, terms, screen, payment, settle, delivery), what this store paid and to whom, the settlement transaction where the seller returned one, the paying field wallet, dated, its evidence hash bound into the purchase certificate's attests field — plus a stable check URL serving the record free forever. Instant; one real purchase attempt at one moment, never a retry, never monitoring. Every artifact carries a cert_id and verifies free at https://scvd.store/api/verify/{cert_id}.
- **Cryptography:** ed25519 signature by this store's key, published at https://scvd.store/.well-known/scvd-signing-key and carried inside every 402
- **Verify:** GET https://scvd.store/api/verify/{cert_id} — free, no account, no rate limit, checkable offline with the published key
- **Price and fulfilment:** $5 USDC fixed, one-off; nothing here charges again by itself, ever — there is no mechanism that could; delivered instantly
- **Does not attest:** Anything about any other moment, any other buyer, or the seller generally — one transaction, once. An unpaid verdict is a statement about this store's published rules (spend cap, sanctions screen, rails carried), never about the seller. Any payment presentation uses the v2 shape only; a v1-only seller's refusal is recorded as exactly that. A lost response or expired authorization does not prove no money moved: payment_attempt retains the reconciliation facts and names an unknown settlement explicitly. Replay byte recovery does not establish artifact truth or usefulness; changed bytes do not establish fresh fulfillment. Never a badge, never a score.

## About this item

Name your x402 endpoint (the url query parameter) and this store walks it the way a paying stranger does: one unpaid GET with our declared field-research User-Agent, your 402 challenge read the way a real buyer reads it, the cheapest Base rail chosen, the payTo screened, a real EIP-3009 authorization signed by our declared field wallet, presented, and whatever happens next written down — settled or refused, receipt returned or absent, goods delivered or an empty 2xx. Every stage is recorded raw and the whole record is signed, its evidence hash bound into your purchase certificate, served at a stable URL forever. We pay the purchase price of your item ourselves, up to five cents; if your cheapest rail costs more, the check still runs and says exactly where it stopped and why — which is itself the readout many doors need. Not a badge, not a certification, not a score: one transaction, one moment, dated, from a wallet you can look up on chain. Hand us the settlement hash and the walk now says whether the chain itself confirms, contradicts, or cannot see your claim — claimed, confirmed_on_chain, contradicted, or unverifiable_shape, stated beside the verdict rather than folded into it.

- **id:** `launch_check`
- **price:** $5 fixed, one-off; nothing here charges again by itself, ever — there is no mechanism that could
- **fulfillment:** delivered instantly
- **buy:** `GET https://scvd.store/api/buy/launch_check?url=<url>` (USDC over x402 v2 on Base, Polygon, Arbitrum, World, Solana, or USDC over MPP (evm/charge) on Base for every shelf item, every publication page and the commission desk)
- **required inputs:** `url` — fill the `<url>` slot above before paying. The bare door `GET https://scvd.store/api/buy/launch_check` quotes free and refuses the paid request without it; no money moves.
- **sample:** https://scvd.store/samples/launch-check.json
- **does not prove:** Anything about any other moment, any other buyer, or the seller generally — one transaction, once. An unpaid verdict is a statement about this store's published rules (spend cap, sanctions screen, rails carried), never about the seller. Any payment presentation uses the v2 shape only; a v1-only seller's refusal is recorded as exactly that. A lost response or expired authorization does not prove no money moved: payment_attempt retains the reconciliation facts and names an unknown settlement explicitly. Replay byte recovery does not establish artifact truth or usefulness; changed bytes do not establish fresh fulfillment. Never a badge, never a score.

House rules: give your x402 endpoint in the url query parameter: https, default port, on the public internet; one real purchase attempt, once, from the declared field wallet (house-ledger.json) — never a retry loop, never a monitor; we pay at most $0.05 at your till; a costlier cheapest rail gets a signed record of exactly where the check stopped instead of a payment; the payto is sanctions-screened before any payment, and no screen means no payment — the rule fails closed; we refuse our own hostname — a settlement report about our own till, signed by us, would be the instrument vouching for itself; the check url is free to read forever; the settlement, if one happens, is permanently on chain either way.

> Five dollars, and we spend our own nickel at your till. What you get is the thing almost no seller has: your buy path, walked for real, written down by the buyer.