Bindings

The specification defines PPX's data model and operations independently of any transport. A binding says how those operations are carried over one concrete protocol, so that two implementations that pick the same binding interoperate without further negotiation.

Binding	Use it when
HTTP	The baseline. Every conforming provider MUST implement it; the others are layered on top.
MCP	An LLM tool-calling client should read preferences as tools/resources.
A2A	Two autonomous agents exchange profile context directly.
AG-UI	A UI needs live consent prompts and grant events streamed to it.
A2UI	An agent drives a rendered surface it does not own.

All bindings share the same consent model: a binding changes the envelope, never the scope of what a grant permits.

Conformance is declared per binding — see Conformance levels.