Define accounts and agents API surface

.changeset/accounts-and-agents.md

@@ -0,0 +1,26 @@
+---
+"adcontextprotocol": minor
+---
+
+Add accounts and agents specification to AdCP protocol.
+
+AdCP now distinguishes three entities in billable operations:
+- **Brand**: Whose products are advertised (identified by brand manifest)
+- **Account**: Who gets billed, what rates apply (identified by `account_id`)
+- **Agent**: Who is placing the buy (identified by authentication token)
+
+New schemas:
+- `account.json`: Billing relationship with rate cards, payment terms, credit limits
+- `list-accounts-request.json` / `list-accounts-response.json`: Discover accessible accounts
+
+Updated schemas:
+- `media-buy.json`: Added account attribution
+- `create-media-buy-request.json`: Added optional `account_id` field
+- `create-media-buy-response.json`: Added account in response
+- `get-products-request.json`: Added optional `account_id` for rate card context
+- `sync-creatives-request.json`: Added optional `account_id` field for creative ownership
+- `sync-creatives-response.json`: Added account attribution in response
+- `list-creatives-response.json`: Added account attribution per creative
+- `creative-filters.json`: Added `account_ids` filter for querying by account
+
+Deprecates the "Principal" terminology in favor of the more precise Account/Agent distinction.

dist/docs/2.5.3/media-buy/advanced-topics/index.mdx

@@ -28,7 +28,7 @@ This approach enables natural language targeting specifications while supporting
 ### Security & Access Control
 Enterprise-grade security features for multi-tenant environments:
 
-- **[Principals & Security](/docs/media-buy/advanced-topics/principals-and-security)** - Multi-tenant security model and access control
+- **[Principals & Security](/dist/docs/2.5.3/media-buy/advanced-topics/principals-and-security)** - Multi-tenant security model and access control
 - **[Policy Compliance](/docs/media-buy/media-buys/policy-compliance)** - Automated compliance checking and enforcement
 
 ### Implementation Architecture

dist/docs/2.5.3/media-buy/media-buys/policy-compliance.mdx

@@ -204,4 +204,4 @@ Policy decisions can trigger Human-in-the-Loop workflows:
 
 - [`get_products`](/docs/media-buy/task-reference/get_products) - Product discovery with policy checks
 - [`create_media_buy`](/docs/media-buy/task-reference/create_media_buy) - Media buy creation with validation
-- [Principals & Security](/docs/media-buy/advanced-topics/principals-and-security) - Authentication and authorization
+- [Principals & Security](/dist/docs/2.5.3/media-buy/advanced-topics/principals-and-security) - Authentication and authorization

docs.json

@@ -84,7 +84,8 @@
                   "docs/building/integration/a2a-response-format",
                   "docs/protocol/get_adcp_capabilities",
                   "docs/building/integration/context-sessions",
-                  "docs/building/integration/authentication"
+                  "docs/building/integration/authentication",
+                  "docs/building/integration/accounts-and-agents"
                 ]
               },
               {
@@ -239,7 +240,7 @@
                   "docs/media-buy/advanced-topics/pricing-models",
                   "docs/media-buy/advanced-topics/targeting",
                   "docs/media-buy/advanced-topics/agentic-execution-engine",
-                  "docs/media-buy/advanced-topics/principals-and-security",
+                  "docs/media-buy/advanced-topics/accounts-and-security",
                   "docs/media-buy/advanced-topics/testing",
                   "docs/media-buy/advanced-topics/orchestrator-design"
                 ]
@@ -513,7 +514,8 @@
                   "docs/building/integration/a2a-response-format",
                   "docs/protocol/get_adcp_capabilities",
                   "docs/building/integration/context-sessions",
-                  "docs/building/integration/authentication"
+                  "docs/building/integration/authentication",
+                  "docs/building/integration/accounts-and-agents"
                 ]
               },
               {
@@ -668,7 +670,7 @@
                   "docs/media-buy/advanced-topics/pricing-models",
                   "docs/media-buy/advanced-topics/targeting",
                   "docs/media-buy/advanced-topics/agentic-execution-engine",
-                  "docs/media-buy/advanced-topics/principals-and-security",
+                  "docs/media-buy/advanced-topics/accounts-and-security",
                   "docs/media-buy/advanced-topics/testing",
                   "docs/media-buy/advanced-topics/orchestrator-design"
                 ]