ACP Integration

Agentic Commerce Protocol — freeform session metadata today, formal extension registration as the forward path.

This section is advisory and non-prescriptive. The illustrations describe current possibilities and limitations rather than canonical shapes. The ACP working group is invited to publish authoritative LCP integration guidance for the protocol.

What it is

An open-source specification for agent-driven commerce checkout, with a formal extensions mechanism. Supports session metadata that accepts arbitrary keys.

Tier A — Available today

ACP checkout-session metadata accepts arbitrary keys (additionalProperties: true). A legalContext entry placed inside session metadata can be published today without coordination. (The checkout links array uses a closed type enum — terms_of_use, privacy_policy, return_policy, and five others — so it cannot carry a custom legal_context link without upstream registration.)

{
  "links": [
    { "type": "terms_of_use", "url": "https://example.com/terms.md" }
  ],
  "metadata": {
    "legalContext": {
      "type": "sha256",
      "value": "0x7f83b165..."
    }
  }
}

Tier B — Forward work

A formal Specification Enhancement Proposal registering legalContext as a first-class extension would give parsers a standardized handling across implementations.

Limitations

Without upstream registration, parsers must fall back to per-implementation conventions. ACP's links array does expose terms URLs (via the built-in terms_of_use / privacy_policy types — the basis for ACP's "URLs only" entry in the protocol comparison), but those links carry no hash-verified integrity guarantee, which is why the atrHash rides in metadata.

Relationship to existing ACP capabilities

The links array continues to serve as the Level 1 (informational) integration point — the terms are discoverable. The legalContext extension upgrades from informational URLs to hash-verified, integrity-protected references; the two compose.

Steward invitation

The ACP working group is invited to register legalContext as a first-class extension and publish guidance on integrity-bearing fields in checkout responses.