The specification is organized into three distinct layers that work together to provide a complete protocol definition:

Layer 1: Canonical Data Model defines the core data structures and message formats that all A2A implementations must understand. These are protocol agnostic definitions expressed as Protocol Buffer messages.

Layer 2: Abstract Operations describes the fundamental capabilities and behaviors that A2A agents must support, independent of how they are exposed over specific protocols.

Layer 3: Protocol Bindings provides concrete mappings of the abstract operations and data structures to specific protocol bindings (JSON-RPC, gRPC, HTTP/REST), including method names, endpoint patterns, and protocol-specific behaviors.

This layered approach ensures that:

• Core semantics remain consistent across all protocol bindings
• New protocol bindings can be added without changing the fundamental data model
• Developers can reason about A2A operations independently of binding concerns
• Interoperability is maintained through shared understanding of the canonical data model

참고: Agent2Agent (A2A) Protocol Specification (DRAFT v1.0)