Introduction

Auto Agent Protocol (AAP) is a strict A2A v1.0 profile that defines the typed automotive data shapes AI agents and car dealerships exchange when they discover, browse, and submit leads.

AAP does not invent a new wire protocol. It rides on top of the A2A (Agent2Agent) specification: every AAP message travels inside an A2A Message.parts[].data value as a typed DataPart. Dealers MAY expose their AAP skills via either A2A binding — JSON-RPC 2.0 or HTTP+JSON/REST. gRPC is out of scope for v0.2.

The extension is identified by a single URI:

https://autoagentprotocol.org/extensions/a2a-automotive-retail/v0.2

A dealer agent declares itself AAP-compliant by listing this URI in capabilities.extensions[] of its A2A agent card and by implementing one or more of the five standard AAP automotive skills. Agents pick the subset they support; AAP RECOMMENDS at least inventory.search + lead.submit for an end-to-end shopping flow, but neither is mandatory.

What AAP standardizes

AAP v0.2 defines a vocabulary of five standard skill IDs that cover the read-and-lead lifecycle of automotive retail. A dealer agent picks whichever subset matches its capabilities — none of the five is individually mandatory.

Skill	Purpose
dealer.information	Dealership profile, rooftops, hours, contact channels, capabilities
inventory.facets	Aggregated counts and ranges over the dealer's inventory
inventory.search	Filtered, paginated inventory queries
inventory.vehicle	Detail view of one specific vehicle (by VIN, stock, or vehicle_id)
lead.submit	Unified consented lead carrying customer info plus optional vehicle of interest, trade-in, and appointment

It does NOT define authentication (v0.2 agents are public by default; auth is left to A2A), payments, financing approval, RFQ/quote workflows, trade-in valuations, or reservations. Future versions MAY extend this surface; v0.2 is intentionally minimal.

Layered architecture

AAP sits as a profile on top of A2A, which itself sits on top of HTTP. AAP never touches the wire format directly — it defines the shape of typed DataParts that A2A bindings carry.

Anything an A2A client already does — message envelopes, task model, error mapping, server-sent events — works unchanged. AAP only specifies the typed payloads inside DataPart.data.

Quick start

A buyer agent talks to a compliant dealer agent in three steps.

1. Discover the agent

Fetch the A2A agent card at the dealer's well-known URL:

curl https://demo-toyota.example.com/.well-known/agent-card.json

Confirm the card lists the AAP extension URI under capabilities.extensions[].uri and exposes at least one supportedInterfaces[] entry whose protocolBinding is JSONRPC or HTTP+JSON.

2. Pick a binding

A2A defines two protocol bindings AAP supports. Both carry identical AAP payloads.

Binding	A2A spec	AAP page
JSON-RPC 2.0	A2A Section 9	JSON-RPC binding
HTTP+JSON	A2A Section 11	REST binding

3. Send a typed AAP message

Wrap an AAP request inside an A2A Message and POST it to the agent endpoint. Below is the simplest call — dealer.information over the HTTP+JSON binding (using the A2A v1.0 wire format):

curl -X POST https://demo-toyota.example.com/a2a/message:send \
  -H "Content-Type: application/json" \
  -d '{
    "message": {
      "messageId": "01HZ9G5N8D1Y4M6SP9C4XKVW3Q",
      "role": "ROLE_USER",
      "parts": [
        {
          "data": { "type": "dealer.information.request" },
          "mediaType": "application/vnd.autoagent.dealer-information-request+json"
        }
      ]
    },
    "configuration": {
      "acceptedOutputModes": ["application/vnd.autoagent.dealer-information-response+json"]
    }
  }'

The dealer agent replies with an A2A Message whose first DataPart.data is an AAP response:

{
  "message": {
    "messageId": "01HZ9G5P2KA8RT9WMS3B4C5D6E",
    "role": "ROLE_AGENT",
    "parts": [
      {
        "data": {
          "type": "dealer.information.response",
          "data": {
            "name": "Demo Auto Group",
            "welcome_message": "Welcome to Demo Auto Group.",
            "rooftops": [
              {
                "name": "Demo Toyota San Francisco",
                "legal_name": "Demo Toyota of San Francisco, LLC",
                "website": "https://demo-toyota.example.com",
                "phones": [
                  { "name": "Sales", "value": "+14155550100" }
                ],
                "address": {
                  "country": "US",
                  "state": "CA",
                  "city": "San Francisco",
                  "address_line_1": "100 Market St",
                  "zip": "94105"
                },
                "timezone": "America/Los_Angeles",
                "capabilities": ["sales", "service", "financing"]
              }
            ]
          }
        },
        "mediaType": "application/vnd.autoagent.dealer-information-response+json"
      }
    ]
  }
}

Where to read next

• Why automotive needs AAP — the gap AAP fills against A2A, ACP, MCP, and ADF.
• A2A profile — how AAP slots into A2A's three-layer architecture.
• Discovery — full agent card example.
• Pricing and FTC compliance — the four pricing fields and why price is the FTC-final out-the-door amount.
• Skills reference — one page per skill with full request/response examples.