L0 — Wire & transport

Wire-and-transport layer of the AdCP stack. JSON-over-HTTP framing, MCP message envelopes, A2A SSE streams, schema validation, language-native type generation.

L0 takes protocol bytes off the wire and turns them into typed in-memory values, or serializes outbound requests against the published schemas. Symmetric on both sides — same primitives, mirrored direction.

What an SDK at L0 must provide

If you’re picking an SDK or porting one to a new language, this is the L0 build target:

• Generated language-native types from the published JSON schemas (one type per request/response pair, plus shared resource types).
• A schema validator wired against the bundled schemas — so adopters can validate inbound and outbound payloads without hand-rolling the schema-loading dance.
• Transport adapters for at least one of {MCP, A2A}; ideally both. These typically wrap upstream protocol SDKs rather than reimplementing them.
• A schema-bundle accessor that finds the right schema files for the active AdCP version without forcing the adopter to hardcode paths.

For the cumulative cross-layer story (what L0+L1+L2+L3 buys you), see the SDK stack reference.

Pages in this layer

• Schemas — schema bundle, supply-chain verification, type generation, version pinning.
• MCP guide — tools/call envelope, JSON-RPC 2.0, transport adapter shape.
• A2A guide — SSE event streams, task framing, artifact extraction.
• A2A response format — A2A wire-format reference.
• MCP response extraction — parsing tools/call responses to typed values.
• A2A response extraction — parsing A2A streams and artifacts.