AI に「クッキー買って」と頼むと何が起きるか — UCP 公式サンプルで購入完了まで

$ uv pip install "a2a-sdk[http-server]"   # 同梱状態では不足していた依存を追加
$ uv run --no-sync business_agent --port 10997
INFO:     Started server process [64218]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://localhost:10997 (Press CTRL+C to quit)

{
  "ucp": {
    "version": "2026-01-23",
    "services": {
      "dev.ucp.shopping": {
        "version": "2026-01-23",
        "a2a": {
          "endpoint": "http://localhost:10999/.well-known/agent-card.json"
        }
      }
    },
    "capabilities": [
      {
        "version": "2026-01-23",
        "spec": "https://ucp.dev/2026-01-23/specification/shopping/checkout",
        "schema": "https://ucp.dev/2026-01-23/schemas/shopping/checkout.json"
      },
      {
        "version": "2026-01-23",
        "spec": "https://ucp.dev/2026-01-23/specification/shopping/fulfillment",
        "schema": "https://ucp.dev/2026-01-23/schemas/shopping/fulfillment.json",
        "extends": "dev.ucp.shopping.checkout"
      }
    ]
  },
  "payment": {
    "handlers": [
      { "id": "example_payment_provider", "name": "example.payment.provider" }
    ]
  }
}

{
  "ucp": {
    "version": "2026-01-23",
    "capabilities": [
      {
        "version": "2026-01-23",
        "spec": "https://ucp.dev/2026-01-23/specification/shopping/checkout",
        "schema": "https://ucp.dev/2026-01-23/schemas/shopping/checkout.json"
      },
      {
        "version": "2026-01-23",
        "spec": "https://ucp.dev/2026-01-23/specification/shopping/fulfillment",
        "schema": "https://ucp.dev/2026-01-23/schemas/shopping/fulfillment.json",
        "extends": "dev.ucp.shopping.checkout"
      },
      {
        "version": "2026-01-23",
        "spec": "https://ucp.dev/2026-01-23/specification/shopping/discount",
        "schema": "https://ucp.dev/2026-01-23/schemas/shopping/discount.json",
        "extends": "dev.ucp.shopping.checkout"
      },
      { "version": "2026-01-23", "extends": "dev.ucp.shopping.checkout" }
    ]
  },
  "payment": {
    "handlers": [
      { "id": "example_payment_provider", "name": "example.payment.provider",
        "instrument_schemas": [ "…/types/card_payment_instrument.json" ] }
    ]
  }
}

# (1) 版の検査: 購買側の版が店舗の版より新しければ拒否する(日付の大小で比較)
client_version = datetime.strptime(client_version, "%Y-%m-%d").date()
merchant_version = datetime.strptime(merchant_version, "%Y-%m-%d").date()
if client_version > merchant_version:
    raise ServerError(error=InternalError(
        message=f"Version {client_version} is not supported. ...",
        data={"code": "VERSION_UNSUPPORTED", "severity": "critical"}))

# (2) 共通 Capability: (name, version) の組が一致するものだけを残す
client_capabilities_set = {
    (capability.name, capability.version.root)
    for capability in client_capabilities
}
common_capabilites = [
    merchant_capability
    for merchant_capability in merchant_capabilities
    if (merchant_capability.name, merchant_capability.version.root)
    in client_capabilities_set
]

# (3) 交渉結果から Checkout のデータ型をセッションごとに合成する
def get_checkout_type(ucp_metadata: UcpMetadata) -> type[Checkout]:
    active_capability_names = {c.name for c in ucp_metadata.capabilities}
    selected_base_models = []
    # UCP_FULFILLMENT_EXTENSION = "dev.ucp.shopping.fulfillment"
    if UCP_FULFILLMENT_EXTENSION in active_capability_names:
        selected_base_models.append(FulfillmentCheckout)
    if UCP_BUYER_CONSENT_EXTENSION in active_capability_names:
        selected_base_models.append(BuyerConsentCheckout)
    if UCP_DISCOUNT_EXTENSION in active_capability_names:
        selected_base_models.append(DiscountCheckout)
    if not selected_base_models:
        return Checkout
    return create_model(
        "DynamicCheckout",
        __base__=tuple(selected_base_models),
        payment=(PaymentResponse, ...),
    )

{
  "id": "e4c1b9d9-1063-4fda-bfcc-627d59020a36",
  "status": "incomplete",
  "currency": "USD",
  "line_items": [
    { "item": { "id": "BISC-001", "title": "Chocochip Cookies", "price": 499 },
      "quantity": 1 }
  ],
  "buyer": null,
  "totals": [
    { "type": "subtotal", "amount": 499 },
    { "type": "total", "amount": 499 }
  ]
}

{
  "status": "ready_for_complete",
  "buyer": { "email": "aclab-test@example.com" },
  "fulfillment": {
    "methods": [ {
      "type": "shipping",
      "destinations": [ {
        "first_name": "直登", "last_name": "鈴木", "postal_code": "100-0001",
        "address_region": "東京都", "address_locality": "千代田区",
        "street_address": "千代田1-1", "address_country": "日本" } ],
      "groups": [ {
        "selected_option_id": "standard",
        "options": [
          { "id": "standard", "title": "Standard Shipping", "carrier": "USPS" },
          { "id": "express", "title": "Express Shipping", "carrier": "FedEx" } ] } ]
    } ]
  },
  "totals": [
    { "type": "subtotal", "amount": 499 },
    { "type": "fulfillment", "amount": 500 },
    { "type": "tax", "amount": 50 },
    { "type": "total", "amount": 1049 }
  ]
}

// → チャット画面から店舗へ
[ { "data": { "action": "complete_checkout" } },
  { "data": { "a2a.ucp.checkout.payment_data": {
        "id": "instr_2", "type": "card",
        "brand": "visa", "last_digits": "8888",
        "handler_id": "example_payment_provider",
        "credential": { "type": "token", "token": "mock_token_87e2083e-…" }
  } } } ]

// ← 店舗からチャット画面へ
{ "status": "completed",
  "payment": { "selected_instrument_id": "instr_2" },
  "order": {
    "id": "ORD-e4c1b9d9-1063-4fda-bfcc-627d59020a36",
    "permalink_url": "https://example.com/order?id=ORD-e4c1b9d9-…" } }

POST / HTTP/1.1            ← 画面の /api を Vite が :10999 へ中継
Content-Type: application/json
UCP-Agent: profile="http://localhost:3000/profile/agent_profile.json"
X-A2A-Extensions: https://ucp.dev/2026-01-23/specification/overview?v=2026-01-23

{"jsonrpc": "2.0", "id": "…", "method": "message/send",
 "params": {"message": {
   "role": "user", "kind": "message",
   "messageId": "…", "contextId": "…",
   "parts": [{"kind": "text", "text": "在庫のあるクッキーを見せて"}]}}}

# 受信時: UCP 拡張の宣言と UCP-Agent ヘッダが無ければ処理しない
if A2A_UCP_EXTENSION_URL not in context.requested_extensions:
    raise ValueError("UCP Extension is required for this agent")
match = re.search(r'profile="([^"]*)"', ucp_agent_header_value)

# 入力の整形(_prepare_input):
# 決済データは Gemini に渡す文字列から抜き取り、セッション状態へ回す
# UCP_PAYMENT_DATA_KEY = "a2a.ucp.checkout.payment_data"
for data_part in data_list:
    for key in [UCP_PAYMENT_DATA_KEY, UCP_RISK_SIGNALS_KEY]:
        if key in data_part:
            value = data_part.pop(key)
            if key == UCP_PAYMENT_DATA_KEY:
                payment_payload[key] = PaymentInstrument.model_validate(value)
            else:
                payment_payload[key] = value
    if data_part:  # 残った {"action": "complete_checkout"} だけを
        query += "\n" + json.dumps(data_part)  # Gemini への入力に足す

# complete_checkout 道具: 決済データはプロンプトではなく状態から読む
payment_data = tool_context.state.get(ADK_PAYMENT_STATE)  # "__payment_data__"
task = mpp.process_payment(
    payment_data[UCP_PAYMENT_DATA_KEY], payment_data[UCP_RISK_SIGNALS_KEY]
)
if task.status.state == TaskState.completed:
    response = store.place_order(checkout_id)  # status="completed"、order を生成
    return {
        UCP_CHECKOUT_KEY: response.model_dump(mode="json"),
        "status": "success",
    }

# after_tool_callback: 道具の結果を退避する
# (after_agent_callback がこれを応答の構造化データ DataPart にする)
ucp_response_keys = [UCP_CHECKOUT_KEY, "a2a.product_results"]
if any(key in tool_response for key in ucp_response_keys):
    tool_context.state[ADK_LATEST_TOOL_RESULT] = tool_response

--- a/a2a/business_agent/src/business_agent/data/ucp.json      (店舗側の名刺: name を補う)
+++ b/a2a/business_agent/src/business_agent/data/ucp.json
@@ -14,13 +14,15 @@
-        "schema": "https://ucp.dev/2026-01-23/schemas/shopping/checkout.json"
+        "schema": "https://ucp.dev/2026-01-23/schemas/shopping/checkout.json",
+        "name": "dev.ucp.shopping.checkout"
       },
       {
         "version": "2026-01-23",
         "spec": "https://ucp.dev/2026-01-23/specification/shopping/fulfillment",
         "schema": "https://ucp.dev/2026-01-23/schemas/shopping/fulfillment.json",
-        "extends": "dev.ucp.shopping.checkout"
+        "extends": "dev.ucp.shopping.checkout",
+        "name": "dev.ucp.shopping.fulfillment"

--- a/a2a/chat-client/profile/agent_profile.json               (購買側の名刺: 同じく name を補う。3 か所)
+++ b/a2a/chat-client/profile/agent_profile.json
+        "name": "dev.ucp.shopping.checkout"
   …
+        "name": "dev.ucp.shopping.fulfillment"
   …
+        "name": "dev.ucp.shopping.discount"

--- a/a2a/chat-client/mocks/credentialProviderProxy.ts          (模擬決済: SDK の型に合わせて複製)
+++ b/a2a/chat-client/mocks/credentialProviderProxy.ts
@@ -104,6 +104,12 @@ export class CredentialProviderProxy {
     return {
       ...payment_method,
+      // ucp-sdk 0.1.0 の CardPaymentInstrument は brand / last_digits を
+      // トップレベルに要求するため、display の内容を複製する
+      brand: payment_method.display.brand,
+      last_digits: payment_method.display.last_digits,
+      expiry_month: payment_method.display.expiry_month,
+      expiry_year: payment_method.display.expiry_year,
       handler_id: this.handler_id,

// A2A 版(2026-01-23)
// capabilities は名前フィールドの無いリスト。決済は ucp の外の payment.handlers
{ "ucp": {
    "version": "2026-01-23",
    "services": { "dev.ucp.shopping": {
        "version": "2026-01-23",
        "a2a": {
          "endpoint": "http://localhost:10999/.well-known/agent-card.json" }
    } },
    "capabilities": [
      { "version": "2026-01-23",
        "spec": "…/checkout", "schema": "…/checkout.json" },
      { "version": "2026-01-23",
        "spec": "…/fulfillment", "schema": "…/fulfillment.json",
        "extends": "dev.ucp.shopping.checkout" } ] },
  "payment": { "handlers": [
      { "id": "example_payment_provider",
        "name": "example.payment.provider", … } ] } }

// REST 版(2026-04-08)
// capabilities は名前をキーにした辞書(版ごとの配列)。決済ハンドラと署名鍵が ucp の中に入る
{ "ucp": {
    "version": "2026-04-08",
    "services": { "dev.ucp.shopping": [ {
        "version": "2026-04-08", "transport": "rest",
        "endpoint": "http://localhost:8182",
        "schema": "…/services/shopping/openapi.json" } ] },
    "capabilities": {
      "dev.ucp.shopping.checkout": [
        { "version": "2026-04-08", "spec": "…", "schema": "…" } ],
      "dev.ucp.shopping.cart":  [ { … } ],
      "dev.ucp.shopping.order": [ { … } ],
      "dev.ucp.shopping.discount": [
        { …, "extends": ["dev.ucp.shopping.checkout",
                         "dev.ucp.shopping.cart"] } ],
      "dev.ucp.shopping.fulfillment": [
        { …, "extends": "dev.ucp.shopping.checkout" } ],
      "dev.ucp.shopping.buyer_consent": [
        { …, "extends": "dev.ucp.shopping.checkout" } ] },
    "payment_handlers": {
      "dev.shopify.shop_pay": [ … ],
      "com.google.pay": [ … ],
      "dev.mock.payment_handler": [ … ] },
    "keys": [ { "kty": "EC", "crv": "P-256", "alg": "ES256", "use": "sig",
                "kid": "…", "x": "…", "y": "…" } ] },
  "signing_keys": [ … ] }