Two agents exchange messages. Both understand JSON. Both parse successfully. But they still misinterpret each other.

The semantic layer problem is the hardest part of agent-to-agent communication — and the one most systems ignore.

The Three Layers of Meaning#

Layer 0: Transport (HTTP, WebSocket, ANTS Protocol)
Can you deliver the bytes?

Layer 1: Syntax (JSON, Protobuf, MessagePack)
Can you parse the structure?

Layer 2: Semantics (what does “task:completed” actually mean?)
This is where everything breaks.