adcontextprotocol · youbek · Nov 13, 2025 · Nov 13, 2025
diff --git a/schemas/cache/1.0.0/activate-signal-request.json b/schemas/cache/1.0.0/activate-signal-request.json
@@ -16,6 +16,11 @@
         "$ref": "destination.json"
       },
       "minItems": 1
+    },
+    "context": {
+      "type": "object",
+      "description": "Initiator-provided context included in the request payload. Agents must echo this value back unchanged in responses and webhooks. Use for UI/session hints, correlation tokens, or tracking metadata.",
+      "additionalProperties": true
     }
   },
   "required": [

diff --git a/schemas/cache/1.0.0/activate-signal-response.json b/schemas/cache/1.0.0/activate-signal-response.json
@@ -15,6 +15,11 @@
           "items": {
             "$ref": "deployment.json"
           }
+        },
+        "context": {
+          "type": "object",
+          "description": "Initiator-provided context echoed inside the task payload. Opaque metadata such as UI/session hints, correlation tokens, or tracking identifiers.",
+          "additionalProperties": true
         }
       },
       "required": [
@@ -38,6 +43,11 @@
             "$ref": "error.json"
           },
           "minItems": 1
+        },
+        "context": {
+          "type": "object",
+          "description": "Initiator-provided context echoed inside the task payload. Opaque metadata such as UI/session hints, correlation tokens, or tracking identifiers.",
+          "additionalProperties": true
         }
       },
       "required": [

diff --git a/schemas/cache/1.0.0/build-creative-request.json b/schemas/cache/1.0.0/build-creative-request.json
@@ -16,6 +16,11 @@
     "target_format_id": {
       "$ref": "format-id.json",
       "description": "Format ID to generate. The format definition specifies required input assets and output structure."
+    },
+    "context": {
+      "type": "object",
+      "description": "Initiator-provided context included in the request payload. Agentsmust echo this value back unchanged in responses and webhooks. Use for UI/session hints, correlation tokens, or tracking metadata.",
+      "additionalProperties": true
     }
   },
   "required": [

diff --git a/schemas/cache/1.0.0/build-creative-response.json b/schemas/cache/1.0.0/build-creative-response.json
@@ -12,6 +12,11 @@
         "creative_manifest": {
           "$ref": "creative-manifest.json",
           "description": "The generated or transformed creative manifest"
+        },
+        "context": {
+          "type": "object",
+          "description": "Initiator-provided context echoed inside the task payload. Opaque metadata such as UI/session hints, correlation tokens, or tracking identifiers.",
+          "additionalProperties": true
         }
       },
       "required": [
@@ -35,6 +40,11 @@
             "$ref": "error.json"
           },
           "minItems": 1
+        },
+        "context": {
+          "type": "object",
+          "description": "Initiator-provided context echoed inside the task payload. Opaque metadata such as UI/session hints, correlation tokens, or tracking identifiers.",
+          "additionalProperties": true
         }
       },
       "required": [

diff --git a/schemas/cache/1.0.0/create-media-buy-request.json b/schemas/cache/1.0.0/create-media-buy-request.json
@@ -75,6 +75,11 @@
           ]
         }
       ]
+    },
+    "context": {
+      "type": "object",
+      "description": "Initiator-provided context included in the request payload. Agentsmust echo this value back unchanged in responses and webhooks. Use for UI/session hints, correlation tokens, or tracking metadata.",
+      "additionalProperties": true
     }
   },
   "required": [

diff --git a/schemas/cache/1.0.0/create-media-buy-response.json b/schemas/cache/1.0.0/create-media-buy-response.json
@@ -43,6 +43,11 @@
             ],
             "additionalProperties": false
           }
+        },
+        "context": {
+          "type": "object",
+          "description": "Initiator-provided context echoed inside the task payload. Opaque metadata such as UI/session hints, correlation tokens, or tracking identifiers.",
+          "additionalProperties": true
         }
       },
       "required": [
@@ -68,6 +73,11 @@
             "$ref": "error.json"
           },
           "minItems": 1
+        },
+        "context": {
+          "type": "object",
+          "description": "Initiator-provided context echoed inside the task payload. Opaque metadata such as UI/session hints, correlation tokens, or tracking identifiers.",
+          "additionalProperties": true
         }
       },
       "required": [

diff --git a/schemas/cache/1.0.0/get-media-buy-delivery-request.json b/schemas/cache/1.0.0/get-media-buy-delivery-request.json
@@ -57,6 +57,11 @@
       "type": "string",
       "pattern": "^\\d{4}-\\d{2}-\\d{2}$",
       "description": "End date for reporting period (YYYY-MM-DD)"
+    },
+    "context": {
+      "type": "object",
+      "description": "Initiator-provided context included in the request payload. Agentsmust echo this value back unchanged in responses and webhooks. Use for UI/session hints, correlation tokens, or tracking metadata.",
+      "additionalProperties": true
     }
   },
   "additionalProperties": false

diff --git a/schemas/cache/1.0.0/get-media-buy-delivery-response.json b/schemas/cache/1.0.0/get-media-buy-delivery-response.json
@@ -180,11 +180,28 @@
                       "type": "number",
                       "description": "Delivery pace (1.0 = on track, <1.0 = behind, >1.0 = ahead)",
                       "minimum": 0
+                    },
+                    "pricing_model": {
+                      "$ref": "pricing-model.json",
+                      "description": "The pricing model used for this package (e.g., cpm, cpcv, cpp). Indicates how the package is billed and which metrics are most relevant for optimization."
+                    },
+                    "rate": {
+                      "type": "number",
+                      "description": "The pricing rate for this package in the specified currency. For fixed-rate pricing, this is the agreed rate (e.g., CPM rate of 12.50 means $12.50 per 1,000 impressions). For auction-based pricing, this represents the effective rate based on actual delivery.",
+                      "minimum": 0
+                    },
+                    "currency": {
+                      "type": "string",
+                      "description": "ISO 4217 currency code (e.g., USD, EUR, GBP) for this package's pricing. Indicates the currency in which the rate and spend values are denominated. Different packages can use different currencies when supported by the publisher.",
+                      "pattern": "^[A-Z]{3}$"
                     }
                   },
                   "required": [
                     "package_id",
-                    "spend"
+                    "spend",
+                    "pricing_model",
+                    "rate",
+                    "currency"
                   ]
                 }
               ]
@@ -236,6 +253,11 @@
       "items": {
         "$ref": "error.json"
       }
+    },
+    "context": {
+      "type": "object",
+      "description": "Initiator-provided context echoed inside the task payload. Opaque metadata such as UI/session hints, correlation tokens, or tracking identifiers.",
+      "additionalProperties": true
     }
   },
   "required": [

diff --git a/schemas/cache/1.0.0/get-products-request.json b/schemas/cache/1.0.0/get-products-request.json
@@ -54,6 +54,11 @@
         }
       },
       "additionalProperties": false
+    },
+    "context": {
+      "type": "object",
+      "description": "Initiator-provided context included in the request payload. Agentsmust echo this value back unchanged in responses and webhooks. Use for UI/session hints, correlation tokens, or tracking metadata.",
+      "additionalProperties": true
     }
   },
   "required": [],

diff --git a/schemas/cache/1.0.0/get-products-response.json b/schemas/cache/1.0.0/get-products-response.json
@@ -18,6 +18,11 @@
       "items": {
         "$ref": "error.json"
       }
+    },
+    "context": {
+      "type": "object",
+      "description": "Initiator-provided context echoed inside the task payload. Opaque metadata such as UI/session hints, correlation tokens, or tracking identifiers.",
+      "additionalProperties": true
     }
   },
   "required": [

diff --git a/schemas/cache/1.0.0/get-signals-request.json b/schemas/cache/1.0.0/get-signals-request.json
@@ -77,6 +77,11 @@
       "type": "integer",
       "description": "Maximum number of results to return",
       "minimum": 1
+    },
+    "context": {
+      "type": "object",
+      "description": "Initiator-provided context included in the request payload. Agents must echo this value back unchanged in responses and webhooks. Use for UI/session hints, correlation tokens, or tracking metadata.",
+      "additionalProperties": true
     }
   },
   "required": [

diff --git a/schemas/cache/1.0.0/get-signals-response.json b/schemas/cache/1.0.0/get-signals-response.json
@@ -90,6 +90,11 @@
       "items": {
         "$ref": "error.json"
       }
+    },
+    "context": {
+      "type": "object",
+      "description": "Initiator-provided context echoed inside the task payload. Opaque metadata such as UI/session hints, correlation tokens, or tracking identifiers.",
+      "additionalProperties": true
     }
   },
   "required": [

diff --git a/schemas/cache/1.0.0/list-authorized-properties-request.json b/schemas/cache/1.0.0/list-authorized-properties-request.json
@@ -14,6 +14,11 @@
         "description": "Publisher domain to filter by (e.g., 'cnn.com', 'espn.com')"
       },
       "minItems": 1
+    },
+    "context": {
+      "type": "object",
+      "description": "Initiator-provided context included in the request payload. Agentsmust echo this value back unchanged in responses and webhooks. Use for UI/session hints, correlation tokens, or tracking metadata.",
+      "additionalProperties": true
     }
   },
   "additionalProperties": false

diff --git a/schemas/cache/1.0.0/list-authorized-properties-response.json b/schemas/cache/1.0.0/list-authorized-properties-response.json
@@ -55,6 +55,11 @@
       "items": {
         "$ref": "error.json"
       }
+    },
+    "context": {
+      "type": "object",
+      "description": "Initiator-provided context echoed inside the task payload. Opaque metadata such as UI/session hints, correlation tokens, or tracking identifiers.",
+      "additionalProperties": true
     }
   },
   "required": [

diff --git a/schemas/cache/1.0.0/list-creative-formats-request.json b/schemas/cache/1.0.0/list-creative-formats-request.json
@@ -61,6 +61,11 @@
     "name_search": {
       "type": "string",
       "description": "Search for formats by name (case-insensitive partial match)"
+    },
+    "context": {
+      "type": "object",
+      "description": "Initiator-provided context included in the request payload. Agentsmust echo this value back unchanged in responses and webhooks. Use for UI/session hints, correlation tokens, or tracking metadata.",
+      "additionalProperties": true
     }
   },
   "additionalProperties": false

diff --git a/schemas/cache/1.0.0/list-creative-formats-response.json b/schemas/cache/1.0.0/list-creative-formats-response.json
@@ -52,6 +52,11 @@
       "items": {
         "$ref": "error.json"
       }
+    },
+    "context": {
+      "type": "object",
+      "description": "Initiator-provided context echoed inside the task payload. Opaque metadata such as UI/session hints, correlation tokens, or tracking identifiers.",
+      "additionalProperties": true
     }
   },
   "required": [

diff --git a/schemas/cache/1.0.0/list-creatives-request.json b/schemas/cache/1.0.0/list-creatives-request.json
@@ -181,6 +181,11 @@
           "sub_assets"
         ]
       }
+    },
+    "context": {
+      "type": "object",
+      "description": "Initiator-provided context included in the request payload. Agentsmust echo this value back unchanged in responses and webhooks. Use for UI/session hints, correlation tokens, or tracking metadata.",
+      "additionalProperties": true
     }
   },
   "additionalProperties": false,

diff --git a/schemas/cache/1.0.0/list-creatives-response.json b/schemas/cache/1.0.0/list-creatives-response.json
@@ -344,6 +344,11 @@
         }
       },
       "additionalProperties": false
+    },
+    "context": {
+      "type": "object",
+      "description": "Initiator-provided context echoed inside the task payload. Opaque metadata such as UI/session hints, correlation tokens, or tracking identifiers.",
+      "additionalProperties": true
     }
   },
   "required": [

diff --git a/schemas/cache/1.0.0/preview-creative-request.json b/schemas/cache/1.0.0/preview-creative-request.json
@@ -56,6 +56,11 @@
           ],
           "default": "url",
           "description": "Output format for previews. 'url' returns preview_url (iframe-embeddable URL), 'html' returns preview_html (raw HTML for direct embedding). Default: 'url' for backward compatibility."
+        },
+        "context": {
+          "type": "object",
+          "description": "Initiator-provided context included in the request payload. Agents must echo this value back unchanged in responses and webhooks. Use for UI/session hints, correlation tokens, or tracking metadata.",
+          "additionalProperties": true
         }
       },
       "required": [
@@ -141,6 +146,11 @@
           ],
           "default": "url",
           "description": "Default output format for all requests in this batch. Individual requests can override this. 'url' returns preview_url (iframe-embeddable URL), 'html' returns preview_html (raw HTML for direct embedding)."
+        },
+        "context": {
+          "type": "object",
+          "description": "Initiator-provided context included in the request payload. Agents must echo this value back unchanged in responses and webhooks. Use for UI/session hints, correlation tokens, or tracking metadata.",
+          "additionalProperties": true
         }
       },
       "required": [

diff --git a/schemas/cache/1.0.0/preview-creative-response.json b/schemas/cache/1.0.0/preview-creative-response.json
@@ -68,6 +68,11 @@
           "type": "string",
           "format": "date-time",
           "description": "ISO 8601 timestamp when preview links expire"
+        },
+        "context": {
+          "type": "object",
+          "description": "Initiator-provided context echoed inside the preview payload. Opaque metadata such as UI/session hints, correlation tokens, or tracking identifiers.",
+          "additionalProperties": true
         }
       },
       "required": [
@@ -204,6 +209,11 @@
             ]
           },
           "minItems": 1
+        },
+        "context": {
+          "type": "object",
+          "description": "Initiator-provided context echoed inside the preview payload. Opaque metadata such as UI/session hints, correlation tokens, or tracking identifiers.",
+          "additionalProperties": true
         }
       },
       "required": [

diff --git a/schemas/cache/1.0.0/protocol-envelope.json b/schemas/cache/1.0.0/protocol-envelope.json
@@ -140,7 +140,7 @@
     "Different protocols may use different serialization formats but maintain the same semantic structure",
     "MCP may represent this via tool response content fields and metadata",
     "A2A may represent this via assistant messages with structured data",
-    "REST may use HTTP headers for status/context and JSON body for payload",
+    "REST may use HTTP headers for status/task metadata and JSON body for payload",
     "The envelope ensures consistent behavior across all protocol implementations"
   ]
 }
diff --git a/schemas/cache/1.0.0/provide-performance-feedback-request.json b/schemas/cache/1.0.0/provide-performance-feedback-request.json
@@ -71,6 +71,11 @@
         "verification_partner"
       ],
       "default": "buyer_attribution"
+    },
+    "context": {
+      "type": "object",
+      "description": "Initiator-provided context included in the request payload. Agentsmust echo this value back unchanged in responses and webhooks. Use for UI/session hints, correlation tokens, or tracking metadata.",
+      "additionalProperties": true
     }
   },
   "required": [

diff --git a/schemas/cache/1.0.0/provide-performance-feedback-response.json b/schemas/cache/1.0.0/provide-performance-feedback-response.json
@@ -13,6 +13,11 @@
           "type": "boolean",
           "description": "Whether the performance feedback was successfully received",
           "const": true
+        },
+        "context": {
+          "type": "object",
+          "description": "Initiator-provided context echoed inside the task payload. Opaque metadata such as UI/session hints, correlation tokens, or tracking identifiers.",
+          "additionalProperties": true
         }
       },
       "required": [
@@ -36,6 +41,11 @@
             "$ref": "error.json"
           },
           "minItems": 1
+        },
+        "context": {
+          "type": "object",
+          "description": "Initiator-provided context echoed inside the task payload. Opaque metadata such as UI/session hints, correlation tokens, or tracking identifiers.",
+          "additionalProperties": true
         }
       },
       "required": [

diff --git a/schemas/cache/1.0.0/sync-creatives-request.json b/schemas/cache/1.0.0/sync-creatives-request.json
@@ -54,6 +54,11 @@
     "push_notification_config": {
       "$ref": "push-notification-config.json",
       "description": "Optional webhook configuration for async sync notifications. Publisher will send webhook when sync completes if operation takes longer than immediate response time (typically for large bulk operations or manual approval/HITL)."
+    },
+    "context": {
+      "type": "object",
+      "description": "Initiator-provided context included in the request payload. Agents must echo this value back unchanged in responses and webhooks. Use for UI/session hints, correlation tokens, or tracking metadata.",
+      "additionalProperties": true
     }
   },
   "required": [