AGTP Merchant Identity and Agentic Commerce Binding

The Agent Transfer Protocol (AGTP) specifies the sending side of an agentic transaction: agent identity, Authority-Scope enforcement, Budget- Limit declaration, and a signed Attribution-Record on every method invocation. The receiving side of a PURCHASE transaction -- the merchant or service provider -- has no equivalent protocol-level identity or verification mechanism. This is the merchant identity gap. This document specifies the AGTP Merchant Identity and Agentic Commerce Binding. It defines the Merchant Manifest Document, a signed identity record structurally parallel to the Agent Manifest Document; the Merchant Genesis, the origin document from which a merchant's canonical identifier is derived; Merchant Trust Tiers aligned with AGTP Trust Tier semantics; and the protocol integration points at which merchant identity is verified. These include the PURCHASE method handshake, the DISCOVER method result surface, and the Attribution-Record. This document also defines the Intent- Assertion header for portable, detached principal- authorized intent, the Cart-Digest mechanism for multi-line-item transactions, and the 455 Counterparty Unverified status code. Together these mechanisms close the verification loop between agent and merchant within AGTP's governance model. Version 01 aligns the merchant identity model with AGTP v05. Merchant Trust Tier 1 now supports three equivalent verification paths (dns- anchored, log-anchored, hybrid) matching the base AGTP verification paths, replacing v00's DNS-only Tier 1 requirement. Version 01 also adopts the Agent Genesis taxonomy introduced in [AGTP-LOG]: the merchant origin document is the Merchant Genesis, superseding the "Merchant Birth Certificate" terminology in v00.