Protocol

UCP

Universal Commerce Protocol

A legal_context link in the checkout carries the ATR hash, before the business signs the checkout. Source: lcp docs: agentic checkouts⁠ (opens in a new tab) The Agentic Transaction Record (ATR) is one record of exactly what was agreed, for one transaction. Its ATR hash, the ATR’s fingerprint, is the proof bound to the transaction: change one byte of the ATR and it no longer matches. Source: lcp docs: the ATR⁠ (opens in a new tab) · Source: lcp docs: the ATR hash⁠ (opens in a new tab)

UCP, the Universal Commerce Protocol, is a project of the UCP Authors. Source: ucp.dev⁠ (opens in a new tab) Integra is not affiliated; we read their published interfaces.

lcp docs: agentic checkouts⁠ (opens in a new tab) · lcp docs: the ATR⁠ (opens in a new tab) · lcp docs: the ATR hash⁠ (opens in a new tab) · ucp.dev⁠ (opens in a new tab)

The protocol’s own site⁠

UCP

Commerce lifecycle

The checkout: A legal_context link carrying the ATR hash, before the business signs the checkout.

Run an agentic transaction over UCP now

A real transaction between Integra-managed agents on a test network, then its proof: the agreed terms, bound to the payment.

Loading the demonstrations…

These are real transactions between Integra-managed agents, using testnet funds. Transactions are settled at 1/10,000th of their stated value, for demonstration purposes.

What it is

UCP is an open standard for the full commerce lifecycle: discovery, catalog, checkout, orders, fulfilment and post-purchase adjustments. Source: LCP §C.3⁠ (opens in a new tab)

LCP §C.3⁠ (opens in a new tab)

Where the ATR hash rides

The checkout carries the ATR hash and a link to the ATR, before the business signs it.

Exhibit Where it rides, in the protocol’s and the package’s terms

The package

The package appends one legal_context entry to the checkout’s links[], carrying the link to the ATR and the ATR hash as its LCP string, before the business signs the checkout. Source: lcp docs: agentic checkouts⁠ (opens in a new tab)

Under UCP’s AP2 Mandates extension, the buyer’s checkout mandate commits to that signed checkout; without it, UCP defines no buyer signature. Source: lcp docs: agentic checkouts⁠ (opens in a new tab)

A UCP checkout paid in x402 goes through the payment handler com.integraledger.lcp.x402, whose specification is an LCP profile published with the package; the x402 payment then carries the ATR hash where its own pairing places it. Source: lcp docs: agentic checkouts⁠ (opens in a new tab)

What a payment through it proves

Each pairing’s record states what a payment through it shows, and what it does not, in the package’s own words. These are read from the package when the site is built. Source: lcp docs: pairings reference⁠ (opens in a new tab)

Of these 4 pairings, 2 have the buyer’s signature cover the ATR hash, 0 leave a public proof of it, and 0 let anyone read it back from the chain alone. Source: lcp docs: pairings reference⁠ (opens in a new tab)

Switch to Technical to see each pairing, and the sentence its record states about what a payment through it proves.

lcp docs: pairings reference⁠ (opens in a new tab)

Exhibit Each pairing’s record

The package

Pattern: Opaque Challenge (LCP §8.3.4)⁠ (opens in a new tab)
What a payment through it proves: Before this payment, the buyer signed and paid an agreement transaction carrying this ATR's hash on <network>, recorded in <transaction>. The booking carried this ATR's hash and link as its legal_context link. The buyer's checkout mandate under UCP's AP2 Mandates extension carries checkout_hash, the SHA-256 of the booking presented beside it, and the hash was read from that booking. The seller did not verify the mandate's signature, or, where an open mandate precedes it in a chain, that mandate's signature, its delegation (cnf) or the chain's link; the PSP verifies the payment mandate over the same booking hash. Settlement is the seller's report. This does not show that amount, payee or timing match the ATR's content.
LCP profile: ucp/checkout/legal-context⁠ (opens in a new tab)
Pattern: HTTP-layer advisory (LCP §8.3.7)⁠ (opens in a new tab)
What a payment through it proves: Before this payment, the buyer signed and paid an agreement transaction carrying this ATR's hash on <network>, recorded in <transaction>. The booking response carried this ATR's hash and link as its legal_context link. UCP without the AP2 Mandates extension defines no buyer signature, so the buyer's approval did not sign the hash. The seller tied the payment to the hash in its report.
LCP profile: ucp/checkout/legal-context⁠ (opens in a new tab)
Pattern: Opaque Challenge (LCP §8.3.4)⁠ (opens in a new tab)
What a payment through it proves: Before this payment, the buyer signed and paid an agreement transaction carrying this ATR's hash on <network>, recorded in <transaction>. The checkout carried this ATR's hash and link as its legal_context link. The buyer's checkout mandate under UCP's AP2 Mandates extension carries checkout_hash, the SHA-256 of the checkout presented beside it, and the hash was read from that checkout. The seller did not verify the mandate's signature, or, where an open mandate precedes it in a chain, that mandate's signature, its delegation (cnf) or the chain's link; the PSP verifies the payment mandate over the same checkout hash. Settlement is the seller's report. This does not show that amount, payee or timing match the ATR's content.
LCP profile: ucp/checkout/legal-context⁠ (opens in a new tab)
Pattern: HTTP-layer advisory (LCP §8.3.7)⁠ (opens in a new tab)
What a payment through it proves: Before this payment, the buyer signed and paid an agreement transaction carrying this ATR's hash on <network>, recorded in <transaction>. The checkout response carried this ATR's hash and link as its legal_context link. UCP without the AP2 Mandates extension defines no buyer signature, so the buyer's approval did not sign the hash. The seller tied the payment to the hash in its report.
LCP profile: ucp/checkout/legal-context⁠ (opens in a new tab)

Where a sentence names <network> and <transaction>, the pairing’s record fills them in: they name the agreement payment the buyer made first. Source: lcp docs: pairings reference⁠ (opens in a new tab) · Source: lcp docs: the agreement URL⁠ (opens in a new tab)

The rails it settles on

A checkout through this protocol is paid by the provider the checkout names, so it lists no rail of its own.

Ready to see your own agreements proved?

Tell us what you sell, buy or carry, and we will show you where the agreement rides in it.

Integra Binder, hosted by Integra, does the seller’s side of each agreement and is free on test networks, with test-network USDC.

Talk to us