Core Concepts

Architecture Overview

Capabilities vs Extensions

ASP defines two kinds of protocol additions:

Capabilities are standalone features that do not depend on UCP schemas:

• dev.asp.services.discovery — Provider search and filtering
• dev.asp.services.catalog — Extended catalogs with modifiers
• dev.asp.services.personalization — User profiles and promotions
• dev.asp.services.reviews — Post-service reviews and ratings

Extensions compose on top of existing UCP schemas using allOf:

• dev.asp.services.fulfillment — Extends dev.ucp.shopping.checkout
• dev.asp.services.order_tracking — Extends dev.ucp.shopping.order
• dev.asp.services.streaming — Extends dev.asp.services.order_tracking

Extensions declare an extends field pointing to the UCP capability they build upon.

Discovery Profiles

Marketplaces declare their ASP support via a /.well-known/asp endpoint that returns a discovery profile:

{
  "asp": {
    "version": "2026-02-19",
    "services": {
      "live_services": {
        "version": "2026-02-19",
        "rest": {
          "schema": "https://example.com/asp/openapi.yaml",
          "endpoint": "https://api.example.com/asp/v1"
        },
        "a2a": {
          "agentCard": "https://example.com/asp/a2a/agent-card.json",
          "endpoint": "https://api.example.com/asp/a2a"
        },
        "websocket": {
          "schema": "https://example.com/asp/asyncapi.yaml",
          "endpoint": "wss://api.example.com/asp/v1/ws"
        }
      }
    },
    "capabilities": [
      { "name": "dev.asp.services.discovery", "version": "2026-02-19" },
      { "name": "dev.asp.services.catalog", "version": "2026-02-19" },
      { "name": "dev.asp.services.fulfillment", "version": "2026-02-19", "extends": "dev.ucp.shopping.checkout" },
      { "name": "dev.asp.services.order_tracking", "version": "2026-02-19", "extends": "dev.ucp.shopping.order" },
      { "name": "dev.asp.services.personalization", "version": "2026-02-19" },
      { "name": "dev.asp.services.streaming", "version": "2026-02-19", "extends": "dev.asp.services.order_tracking" },
      { "name": "dev.asp.services.reviews", "version": "2026-02-19" }
    ]
  }
}

Schema Composition

Extensions use JSON Schema's allOf to layer additional properties onto UCP schemas without replacing them:

{
  "allOf": [
    { "$ref": "https://ucp.dev/schemas/shopping/checkout.json" },
    {
      "type": "object",
      "properties": {
        "fulfillment": { "$ref": "fulfillment.json" },
        "loyalty": { "$ref": "loyalty_discount.json" }
      }
    }
  ]
}

This means any UCP-compliant checkout remains valid — ASP adds optional fields alongside.

Domain Profiles

ASP core schemas are vertical-agnostic. For vertical-specific specialization, domain profiles in spec/schemas/domains/ constrain and extend core types using allOf:

• Food Delivery — Adds cuisine types, dietary restrictions
• Ride-Hailing — Adds vehicle categories, pickup/dropoff locations
• Travel — Adds accommodation categories, check-in/check-out dates

Domain profiles are reference examples, not required by the protocol.

Transport Bindings

ASP schemas can be served over:

• REST — OpenAPI 3.1 binding with standard HTTP methods (request-response)
• MCP — Model Context Protocol for direct agent integration (tool-calling)
• A2A — Agent-to-Agent protocol for multi-step task delegation between agents
• WebSocket — AsyncAPI 3.0 binding for continuous live tracking (streaming)

Transport	Spec File	Pattern	Use Case
REST	openapi.yaml	Request-response	Human apps, polling
MCP	mcp_openrpc.json	JSON-RPC tools	AI agent integration
A2A	a2a_agent_card.json	Task delegation	Agent-to-agent orchestration
WebSocket	asyncapi.yaml	Persistent stream	Live map tracking, real-time ETA

All transport bindings live in source/services/live_services/ and reference the same underlying ASP schemas. The WebSocket binding streams tracking_stream_event messages (location updates, status changes, heartbeats) over a persistent connection, enabling live delivery map rendering.

Versioning

• Protocol version: YYYY-MM-DD format (e.g. 2026-02-19)
• Capability names: Reverse-domain notation (e.g. dev.asp.services.discovery)
• Backwards compatibility: New optional fields can be added without a version bump. Required field changes or removals require a new version.

Relationship to UCP

ASP orchestrates the full transaction lifecycle for live services — from discovering a provider through to post-order reviews. UCP handles the purchase step within that lifecycle: cart management, checkout, and payment.

Phase	Protocol	Steps
Pre-purchase	ASP	Discovery, Catalog, Personalization
Purchase	UCP (with ASP Fulfillment extension)	Cart, Checkout, Payment
Post-purchase	ASP	Order Tracking, Live Streaming, Reviews

ASP's extensions compose onto UCP schemas using allOf, so any UCP-compliant checkout remains valid. An agent that speaks both ASP and UCP can orchestrate a complete live service transaction end-to-end.