Universal-Commerce-Protocol · yanheChen · Jan 16, 2026 · Jan 16, 2026 · Jan 16, 2026 · Jan 16, 2026
diff --git a/docs/documentation/schema-authoring.md b/docs/documentation/schema-authoring.md
@@ -145,7 +145,6 @@ independently negotiated.
 Examples:
 
 - `schemas/shopping/payment.json` — Payment configuration (part of checkout)
-- `schemas/shopping/payment_data.json` — Payment submission data
 
 ### Type Schemas
 

diff --git a/docs/index.md b/docs/index.md
@@ -230,7 +230,8 @@ image: assets/banner.png
           "destinations": [
             {
               "id": "dest_1",
-              "full_name": "Elisa Beckett",
+              "first_name": "Elisa",
+              "last_name": "Beckett",
               "street_address": "1600 Amphitheatre Pkwy",
               "address_locality": "Mountain View",
               "address_region": "CA",
@@ -335,7 +336,8 @@ image: assets/banner.png
           "line_items": [{ "id": "li_1", "quantity": 1 }],
           "method_type": "shipping",
           "destination": {
-            "full_name": "Elisa Beckett",
+            "first_name": "Elisa",
+            "last_name": "Beckett",
             "street_address": "1600 Amphitheatre Pkwy",
             "address_locality": "Mountain View",
             "address_region": "CA",

diff --git a/docs/specification/ap2-mandates.md b/docs/specification/ap2-mandates.md
@@ -198,7 +198,7 @@ Mandates are **SD-JWT** credentials with Key Binding (`+kb`). The platform
 | Mandate | UCP Placement | Purpose |
 | :------ | :------------ | :------ |
 | **checkout_mandate** | `ap2.checkout_mandate` | Proof bound to checkout terms, protects business |
-| **payment_mandate** | `payment_data.token` | Proof bound to payment authorization, protects funds |
+| **payment_mandate** | `payment.instruments[*].credential.token` | Proof bound to payment authorization, protects funds |
 
 The checkout mandate **MUST** contain the full checkout response including the
 `ap2.merchant_authorization` field. This creates a nested cryptographic binding
@@ -235,7 +235,7 @@ a completion request without mandates **MUST** result in a session failure.
 The platform initiates the session. The business returns the `Checkout` object
 with `ap2.merchant_authorization` embedded in the response body.
 
-{{ extension_schema_fields('ap2_mandate.json#/$defs/checkout_response_with_ap2', 'ap2-mandates') }}
+{{ extension_schema_fields('ap2_mandate.json#/$defs/checkout', 'ap2-mandates') }}
 
 **Example Response:**
 ```json
@@ -321,36 +321,40 @@ Binding (+kb) signature.
 Once the mandates are generated, the platform submits them in the completion
 request:
 
-{{ extension_schema_fields('ap2_mandate.json#/$defs/complete_request_with_ap2', 'ap2-mandates') }}
+{{ extension_schema_fields('ap2_mandate.json#/$defs/ap2_with_checkout_mandate', 'ap2-mandates') }}
 
 ```json
 {
-  "payment_data": {
-      "id": "instr_1",
-      "handler_id": "gpay",
-      "type": "card",
-      "description": "Visa •••• 1234",
-      "billing_address": {
-        "street_address": "123 Main St",
-        "address_locality": "Anytown",
-        "address_region": "CA",
-        "address_country": "US",
-        "postal_code": "12345"
-      },
-      "credential": {
-        "type": "PAYMENT_GATEWAY",
-        "token": "examplePaymentMethodToken"
+  "payment": {
+    "instruments": [
+      {
+        "id": "instr_1",
+        "handler_id": "gpay",
+        "type": "card",
+        "rich_text_description": "Visa •••• 1234",
+        "billing_address": {
+          "street_address": "123 Main St",
+          "address_locality": "Anytown",
+          "address_region": "CA",
+          "address_country": "US",
+          "postal_code": "12345"
+        },
+        "credential": {
+          "type": "PAYMENT_GATEWAY",
+          "token": "examplePaymentMethodToken"
+        }
       }
+    ]
   },
   "ap2": {
-     "checkout_mandate": "eyJhbGciOiJFUzI1NiIsInR5cCI6InZjK3NkLWp3dCJ9..." // The User-Signed SD-JWT+kb / platform provider signed SD-JWT / delegated SD-JWT-KB
+    "checkout_mandate": "eyJhbGciOiJFUzI1NiIsInR5cCI6InZjK3NkLWp3dCJ9..." // The User-Signed SD-JWT+kb / platform provider signed SD-JWT / delegated SD-JWT-KB
   }
 }
 ```
 
 *   `ap2.checkout_mandate`: The SD-JWT+kb checkout mandate containing the
     full checkout (with `ap2.merchant_authorization`)
-*   `payment_data.token`: Contains the payment mandate (composite token)
+*   `payment.instruments[*].credential.token`: Contains the payment mandate (composite token)
 
 ## Verification & Processing
 
@@ -405,19 +409,19 @@ checkout.
 
 ### AP2 Checkout Response
 
-The `ap2` object included in CREATE / UPDATE checkout responses.
+The `ap2` object included in checkout responses.
 
-{{ extension_schema_fields('ap2_mandate.json#/$defs/ap2_checkout_response', 'ap2-mandates') }}
+{{ extension_schema_fields('ap2_mandate.json#/$defs/ap2_with_merchant_authorization', 'ap2-mandates') }}
 
-### AP2 Complete Request
+### Checkout Mandate
 
-The `ap2` object included in COMPLETE checkout requests.
+{{ extension_schema_fields('ap2_mandate.json#/$defs/checkout_mandate', 'ap2-mandates') }}
 
-{{ extension_schema_fields('ap2_mandate.json#/$defs/ap2_complete_request', 'ap2-mandates') }}
+### AP2 Complete Request
 
-### Checkout Mandate
+The `ap2` object included in COMPLETE checkout requests.
 
-{{ extension_schema_fields('ap2_mandate.json#/$defs/checkout_mandate', 'ap2-mandates') }}
+{{ extension_schema_fields('ap2_mandate.json#/$defs/ap2_with_checkout_mandate', 'ap2-mandates') }}
 
 ### Error Codes
 

diff --git a/docs/specification/checkout-mcp.md b/docs/specification/checkout-mcp.md
@@ -111,7 +111,8 @@ Maps to the [Create Checkout](checkout.md#create-checkout) operation.
 
 #### Input Schema
 
-*   [Checkout](checkout.md#create-checkout) object.
+*   `checkout` ([Checkout](checkout.md#create-checkout)): **Required**. Contains
+    the initial checkout session data and optional extensions.
     *   Extensions (Optional):
         *   `dev.ucp.shopping.buyer_consent`: [Buyer Consent](buyer-consent.md)
         *   `dev.ucp.shopping.fulfillment`: [Fulfillment](fulfillment.md)
@@ -319,7 +320,7 @@ Maps to the [Get Checkout](checkout.md#get-checkout) operation.
 
 #### Input Schema
 
-*   `id` (String): The ID of the checkout session.
+*   `id` (String): **Required**. The ID of the checkout session.
 
 #### Output Schema
 
@@ -331,8 +332,9 @@ Maps to the [Update Checkout](checkout.md#update-checkout) operation.
 
 #### Input Schema
 
-*   `id` (String): The ID of the checkout session to update.
-*   [Checkout](checkout.md#update-checkout) object.
+*   `id` (String): **Required**. The ID of the checkout session to update.
+*   `checkout` ([Checkout](checkout.md#update-checkout)): **Required**.
+    Contains the updated checkout session data.
     *   Extensions (Optional):
         *   `dev.ucp.shopping.buyer_consent`: [Buyer Consent](buyer-consent.md)
         *   `dev.ucp.shopping.fulfillment`: [Fulfillment](fulfillment.md)
@@ -538,10 +540,10 @@ Maps to the [Complete Checkout](checkout.md#complete-checkout) operation.
 
 #### Input Schema
 
-*   `id` (String): The ID of the checkout session.
-*   `payment` ([Payment](checkout.md#payment), Optional): Payment instrument instance submitted
-    by the buyer.
-*   `idempotency_key` (String, UUID): **Required**. Unique key for retry
+*   `id` (String): **Required**. The ID of the checkout session.
+*   `checkout` ([Checkout](checkout.md#complete-checkout)): **Required**.
+    Contains payment credentials and other finalization data to execute the transaction.
+ *  `idempotency_key` (String, UUID): **Required**. Unique key for retry
     safety.
 
 #### Output Schema

diff --git a/docs/specification/checkout-rest.md b/docs/specification/checkout-rest.md
@@ -761,25 +761,29 @@ place to set these expectations via `messages`.
     Content-Type: application/json
 
     {
-      "payment_data": {
-        "id": "pi_gpay_5678",
-        "handler_id": "com.google.pay",
-        "type": "card",
-        "brand": "mastercard",
-        "last_digits": "5678",
-        "rich_card_art": "https://cart-art-1.html",
-        "rich_text_description": "Google Pay •••• 5678",
-        "billing_address": {
-          "street_address": "123 Main St",
-          "address_locality": "Anytown",
-          "address_region": "CA",
-          "address_country": "US",
-          "postal_code": "12345"
-        },
-        "credential": {
-          "type": "PAYMENT_GATEWAY",
-          "token": "examplePaymentMethodToken"
-        }
+      "payment": {
+        "instruments": [
+          {
+            "id": "pi_gpay_5678",
+            "handler_id": "com.google.pay",
+            "type": "card",
+            "brand": "mastercard",
+            "last_digits": "5678",
+            "rich_card_art": "https://cart-art-1.html",
+            "rich_text_description": "Google Pay •••• 5678",
+            "billing_address": {
+              "street_address": "123 Main St",
+              "address_locality": "Anytown",
+              "address_region": "CA",
+              "address_country": "US",
+              "postal_code": "12345"
+            },
+            "credential": {
+              "type": "PAYMENT_GATEWAY",
+              "token": "examplePaymentMethodToken"
+            }
+          }
+        ]
       },
       "risk_signals": {
         //... risk signal related data (device fingerprint / risk token)

diff --git a/docs/specification/examples/business-tokenizer-payment-handler.md b/docs/specification/examples/business-tokenizer-payment-handler.md
@@ -186,17 +186,22 @@ UCP-Agent: profile="https://platform.example/profile"
 Content-Type: application/json
 
 {
-  "payment_data": {
-    "handler_id": "processor_tokenizer",
-    "type": "card",
-    "brand": "visa",
-    "last_digits": "1111",
-    "expiry_month": 12,
-    "expiry_year": 2026,
-    "credential": {
-      "type": "token",
-      "token": "tok_a1b2c3d4e5f6"
-    }
+  "payment": {
+    "instruments": [
+      {
+        "id": "instr_1",
+        "handler_id": "processor_tokenizer",
+        "type": "card",
+        "brand": "visa",
+        "last_digits": "1111",
+        "expiry_month": 12,
+        "expiry_year": 2026,
+        "credential": {
+          "type": "token",
+          "token": "tok_a1b2c3d4e5f6"
+        }
+      }
+    ]
   },
   "risk_signal": {
     // ... the key value pair for potential risk signal data

diff --git a/docs/specification/examples/encrypted-credential-handler.md b/docs/specification/examples/encrypted-credential-handler.md
@@ -208,20 +208,24 @@ UCP-Agent: profile="https://platform.example/profile"
 Content-Type: application/json
 
 {
-  "payment_data": {
-    "id": "instr_1",
-    "handler_id": "platform_encrypted",
-    "type": "card",
-    "brand": "visa",
-    "last_digits": "1111",
-    "expiry_month": 12,
-    "expiry_year": 2026,
-    "credential": {
-      "type": "encrypted",
-      "encrypted_data": "base64-encoded-encrypted-payload..."
-    }
+  "payment": {
+    "instruments": [
+      {
+        "id": "instr_1",
+        "handler_id": "platform_encrypted",
+        "type": "card",
+        "brand": "visa",
+        "last_digits": "1111",
+        "expiry_month": 12,
+        "expiry_year": 2026,
+        "credential": {
+          "type": "encrypted",
+          "encrypted_data": "base64-encoded-encrypted-payload..."
+        }
+      }
+    ]
   },
-  "risk_signal": {
+  "risk_signals": {
     // ... the key value pair for potential risk signal data
   }
 }

diff --git a/docs/specification/examples/platform-tokenizer-payment-handler.md b/docs/specification/examples/platform-tokenizer-payment-handler.md
@@ -280,18 +280,22 @@ POST /checkout-sessions/{checkout_id}/complete
 Content-Type: application/json
 
 {
-  "payment_data": {
-    "id": "instr_1",
-    "handler_id": "platform_wallet",
-    "type": "card",
-    "brand": "visa",
-    "last_digits": "4242",
-    "credential": {
-      "type": "token",
-      "token": "ptok_x9y8z7w6v5u4"
-    }
+  "payment": {
+    "instruments": [
+      {
+        "id": "instr_1",
+        "handler_id": "platform_wallet",
+        "type": "card",
+        "brand": "visa",
+        "last_digits": "4242",
+        "credential": {
+          "type": "token",
+          "token": "ptok_x9y8z7w6v5u4"
+        }
+      }
+    ]
   },
-  "risk_signal": {
+  "risk_signals": {
     // ... the key value pair for potential risk signal data
   }
 }