Nomotic, Inc. AI agents and agentic systems generate a growing volume of intent- driven, unstructured, and undifferentiated traffic that flows through HTTP indistinguishably from human-initiated requests. HTTP lacks the semantic vocabulary, observability primitives, and identity mechanisms required by agent systems operating at scale. Existing protocols described as Agent Group Messaging Protocols (AGMP), including MCP, ACP, A2A, and ANP, are messaging-layer constructs that presuppose HTTP as their transport. They do not address the underlying transport problem. This document defines the Agent Transfer Protocol (AGTP): a dedicated application-layer protocol for AI agent traffic. Version 04 introduces normative integration hooks for the AGTP Merchant Identity and Agentic Commerce Binding specification [AGTP-MERCHANT], which defines the merchant-side identity model that complements AGTP's agent-side identity model. Version 04 adds four merchant-related request headers (Merchant-ID, Merchant-Manifest-Fingerprint, Intent- Assertion, Cart- Digest), the 455 Counterparty Unverified status code, and the merchant and intent Authority-Scope domains. Together these elements close the verification loop between the initiating agent and the receiving merchant on AGTP PURCHASE invocations. Version 03 introduced normative integration with the Agentic Grammar and Interface Specification (AGIS) [AGIS], which defines the grammar- based validation pathway for AGTP method identifiers. AGIS- conformant methods are accepted at the transport layer via the Method-Grammar header without requiring prior IANA registration, enabling organizations to define domain-specific Agentive API vocabularies while preserving interoperability through shared grammatical constraints. AGTP provides agent-native intent methods (QUERY, SUMMARIZE, BOOK, SCHEDULE, LEARN, DELEGATE, COLLABORATE, CONFIRM, ESCALATE, NOTIFY, DESCRIBE, SUSPEND), protocol-level agent identity and authority headers, and a status code vocabulary designed for the conditions AI agent systems encounter. AGTP SHOULD prefer QUIC for new implementations and MUST support TCP/TLS for compatibility and fallback. It is designed to be composable with existing agent frameworks, not to replace them. Version 02 introduces capability discovery (DESCRIBE), resource budget signaling and enforcement, optional RATS-aligned execution attestation, observability hooks, network zone isolation, session suspension as a method, and normative composition profiles with AGMP (Agent Group Messaging Protocols). Version 02 enables dynamic capability negotiation and resource-aware governance.