The interoperability goal
Imagine a buyer agent running in Indonesia. It discovers a merchant agent that claims to represent a European shop. The buyer agent should not have to trust a chat message, a logo, or a private integration promise. It should be able to inspect public machine-readable evidence.
That is the job of ADI. The merchant agent can live in the merchant shop, use its own runtime, and speak to other agents through A2A. ADI provides the independent trust layer that lets outsiders verify who the agent is, which merchant stands behind it, and what authority has been delegated to it.
The four pieces that must not be mixed up
AgentCard is discovery: where the agent is, which protocol it speaks, which transport authentication it supports, and where trust evidence can be found.
Trust profile is identity binding: the agent DID, the operator, the organization, publication status, ownership proof, and public verification signals.
Credentials are portable authority: signed verifiable credentials such as AP2AgentDelegationCredential, AP2MerchantCredential, and AP2ProductOfferingCredential.
Platform permissions are internal enforcement: ADI scopes such as PAYMENT_PROCESSING decide what the agent may do inside ADI APIs, but the external proof is expressed as signed claims.
How the verification flow works
External buyer agent verifies an ADI merchant agent
The external agent first discovers the A2A surface, then follows the ADI trust-chain links before it relies on a merchant offer or AP2 payment flow.
sequenceDiagram
participant Foreign as External buyer agent
participant Card as Public AgentCard
participant Trust as ADI trust profile
participant Creds as ADI credential manifest
participant Merchant as Merchant agent
participant Pay as Merchant payment rail
Foreign->>Card: Fetch /.well-known/agents/{agentId}/card.json
Card-->>Foreign: A2A endpoint, DID, auth schemes, trust-chain links
Foreign->>Trust: Read public trust profile
Trust-->>Foreign: Agent DID, merchant binding, verification state
Foreign->>Creds: Fetch credential manifest
Creds-->>Foreign: Signed credentials and verification URLs
Foreign->>Foreign: Verify issuer, subject DID, status, expiry, and claims
Foreign->>Merchant: Send AP2/A2A request with mandate evidence
Merchant->>Trust: Validate mandate, catalog, policy, and credential binding
Trust-->>Merchant: Approved or rejected with reason
Merchant->>Pay: Create merchant acquiring payment intent if approved Why OAuth is not enough
OAuth, OIDC, API keys, and JWTs answer a transport question: is this caller allowed to use this endpoint? They do not prove that the agent is legally or commercially allowed to sell a product, represent a merchant, accept a payment, or bind a transaction to a mandate.
ADI keeps those layers separate. A merchant agent can require OAuth or JWT for the channel, but the buyer agent still checks the DID, public trust profile, credential manifest, credential signatures, credential status, and AP2 mandates before relying on the transaction.
What an external agent should check
The AgentCard must use public URLs, not internal Docker hostnames or localhost-only infrastructure.
The trust-chain extension must point to the public AgentCard, trust profile, credential manifest, and credential verification surface.
The credential subject DID must match the agent DID in the AgentCard and trust profile.
The credential issuer, status, expiry, and proof must verify before the external agent treats the merchant claim as real.
For commerce, AP2 mandates and merchant catalog checks must still pass for the specific cart, price, payment rail, and receipt path.
The ADI operating model
This keeps ADI interoperable. ADI agents can buy outside ADI using prepaid issuing-card controls. ADI merchant agents can accept payment through the merchant acquiring rail. External agents can participate if they bring verifiable mandate and credential evidence that ADI can evaluate.
The result is not a closed platform. It is a public trust layer that lets independent agents discover, verify, transact, and explain their decisions to the humans and organizations behind them.