ACP Integration

This section is advisory.

ACP (Agentic Commerce Protocol) is an open-source specification (Apache 2.0) co-maintained by OpenAI and Stripe. Version 2026-01-30 introduced a formal extensions mechanism.

We recommend submitting a Specification Enhancement Proposal (SEP) to register LCP as a formal ACP extension, rather than using freeform session metadata.

Extension Declaration

The legalContext extension would be declared in capabilities.extensions[] during session establishment and negotiated between agent and seller:

{
  "capabilities": {
    "extensions": ["com.integra.legal-context"]
  }
}

Checkout Session with Extension

Once the extension is negotiated, the checkout session includes the legalContext field:

{
  "legalContext": {
    "type": "sha256",
    "value": "0x7f83b165..."
  }
}

Relationship to ACP's Existing links Array

ACP checkout responses already include a links array with terms_of_use, privacy_policy, and return_policy as plain URLs. The LCP extension upgrades these from informational URLs to hash-verified, integrity-protected terms references. The links array continues to serve as the Level 1 (informational) integration point; the legalContext extension adds Level 2+ capabilities.

Integration Flow

1. Seller declares com.integra.legal-context extension in capabilities.extensions[] during session establishment
2. Agent recognizes the extension during negotiation
3. Service creates a checkout session with legalContext
4. Agent reads the legalContext from the session
5. Agent resolves the reference (fetches and verifies the terms)
6. Agent completes checkout

The legal context reference travels with the checkout session through the entire lifecycle. Both parties must support the extension — an agent that does not recognize the legalContext extension will ignore it, and a seller that does not declare it will not include it.