Reading any protocol

readAdvertisedTerms works across all nine registered protocols, because the reference is read out of each one's own placement manifest.

When you only need to know what a document advertises — not to gate a payment — one call covers every registered protocol:

import { readAdvertisedTerms } from "@integraledger/agent-guard";

declare const wire: unknown;

const advertised = readAdvertisedTerms("ucp", wire);
// advertised.protocol           — the protocol whose manifest was used
// advertised.advertisedAtrHash  — `0x${string}`, reconciled across every integrity carrier
// advertised.legalContextUrl    — a union: read | no-field-declared | declared-fields-empty

Nine protocols work and none is listed in the implementation, because the reference is read out of each protocol's own PlacementManifest — every carrier it declares, not the first one that answers.

Handling the terms-URL union

import { readAdvertisedTerms } from "@integraledger/agent-guard";

declare const wire: unknown;

const { legalContextUrl } = readAdvertisedTerms("acp", wire);

switch (legalContextUrl.kind) {
  case "read":
    // legalContextUrl.url — a declared slot carried it; where several were declared, they agreed
    break;
  case "no-field-declared":
    // A fact about the PROTOCOL: it has nowhere to put a locator.
    // No document of this protocol can be faulted for lacking one.
    break;
  case "declared-fields-empty":
    // A fact about THIS DOCUMENT: the protocol has room and this seller left every slot empty.
    // legalContextUrl.fields — which slots were checked
    break;
}

Reporting declared-fields-empty as no-field-declared would blame a protocol for a seller's silence. That is why a bare undefined was not good enough.

This union used to carry a fourth state, undeclared-at-answering-carrier, and it is gone because the defect that required it is fixed. The manifest's terms-URL member was singular, so x402 could declare only one of its two slots. It is plural now, every declared slot is read and reconciled, and a slot riding a container the placement owns is declared on that container — so there is no carrier a declaration fails to reach, and the state is unreachable rather than merely unused.

What it refuses

readAdvertisedTerms throws rather than answering vaguely:

Refuses when	Because
no placement is registered for the protocol	this build cannot read that protocol's documents at all
no declared integrity carrier advertises anything	the message names every slot that was checked
two integrity carriers advertise different references	a seller could otherwise advertise different terms to different readers
the reference is not a `sha256` carrier	the advertised value is compared against a recomputed record hash, and only a hash can be
the placement's own extract refuses	the document carries no readable advertisement; the code and detail are carried through

Integrity carriers only

The reference walk is the buyer's rule, not the placement's: a discovery link locates a standing page and attests nothing, so it is never a candidate here — even though the placement will happily read one.

UCP's links[type=terms_of_service] is the concrete case. It is skipped rather than accepted as a weaker answer. See a located-but-unattested carrier is not a reference.

The terms URL is the placement's rule, because every fact about it belongs to the manifest — which slots a protocol declares, that a slot riding a container the placement owns is addressed through that container, that two slots disagreeing is a refusal rather than a preference. A second implementation here could only agree with it until the day it did not.

Namespaced placements

One protocol's placement is namespaced under the deployment's own reverse domain — Mastercard VI, whose custom Layer-2 constraint type has no default.

import { readAdvertisedTerms } from "@integraledger/agent-guard";

declare const wire: unknown;

readAdvertisedTerms("mastercard-vi", wire, { reverseDomain: "com.example" });

Omitting it there throws from the registry rather than answering about some invented namespace. The other eight placements are singletons and need nothing.

What this does not give you

An AdvertisedTerms is not a GateProposal. It has no offer, so it cannot be handed to transact or evaluate.

If you need to gate a payment on a protocol outside the parseable four, you supply the offer yourself and build the proposal in your own client — the amount and unit are yours to name, because no manifest declares them. See protocol coverage.