Protocol watch

What Legible tracks, and since when.

Agentic commerce changes monthly. This page lists the protocol versions and agent lists every scan is evaluated against, and what changed.

Universal Commerce Protocol

2026-08-25

Profile at /.well-known/ucp. Validated: version format, services and transports, capabilities with spec and schema URLs, payment handlers, signing keys.

ucp.dev

Agentic Commerce Protocol

Signal

Merchant onboarding happens through OpenAI with a product feed, so there is nothing public to validate. Legible checks the prerequisites it can see.

agenticcommerce.dev

AI agents in robots.txt

17

Search, user-triggered and training agents, each checked against its vendor's documentation. Last checked 2026-10-07.

See the full list

UCP versions recognised

2026-08-25 Current Multi-vertical refactor (shopping, food, lodging), 3DS2 via actions, split payments, independent capability versioning.
2026-04-08 Accepted Cart capability, catalog search and lookup, request signing, OAuth 2.0 identity linking scopes, discount on cart.
2026-01-23 Accepted Stability and packaging fixes.
2026-01-11 Accepted Initial public release: checkout, identity linking, orders, versioning framework.

Changelog

  1. 2026-10-07 Legible

    Agent list re-checked against vendor documentation: 17 agents across OpenAI, Anthropic, Perplexity, Google, Microsoft, Apple, Amazon, Meta, Common Crawl and ByteDance.

  2. 2026-08-25 UCP

    UCP 2026-08-25 released: multi-vertical refactor (shopping, food, lodging), 3D Secure through actions, split payments, independent capability versioning. Legible validates against this shape and treats it as current.

  3. 2026-04-08 UCP

    UCP 2026-04-08: cart capability, catalog search and lookup, request signing, OAuth 2.0 identity-linking scopes, discounts on cart. Profiles on this version pass with a "not latest" note.

  4. 2026-03 ACP

    OpenAI moves checkout back to merchant sites and focuses ChatGPT shopping on discovery. Legible scores ACP as prerequisites (crawl access, product data, feed source), not as enrolment.

  5. 2026-01-23 UCP

    UCP 2026-01-23: stability and packaging fixes.

  6. 2026-01-11 UCP

    UCP initial public release, announced by Google in January 2026 with retail and payments partners.

  7. 2025-09 ACP

    OpenAI and Stripe publish the Agentic Commerce Protocol; Instant Checkout launches in ChatGPT.