feat: Add AdCP 2.5 extension to A2A agent card

pyproject.toml

@@ -6,7 +6,7 @@ readme = "README.md"
 requires-python = ">=3.12"
 
 dependencies = [
-    "adcp==2.12.0", # Official AdCP Python client for external agent communication and adagents.json validation
+    "adcp==2.12.1", # Official AdCP Python client for external agent communication and adagents.json validation
     "fastmcp>=2.13.0", # Required for context.get_http_request() support
     "google-generativeai>=0.5.4",
     "google-cloud-iam>=2.19.1",

src/a2a_server/README.md

@@ -101,6 +101,31 @@ Automatically fetches and parses Agent Cards to:
 - Get correct RPC endpoint URLs
 - Display agent metadata and descriptions
 
+### AdCP 2.5 Extension Support
+
+The agent card includes the AdCP extension (per AdCP 2.5 spec) in `capabilities.extensions`:
+
+```json
+{
+  "capabilities": {
+    "extensions": [
+      {
+        "uri": "https://adcontextprotocol.org/schemas/2.5.0/protocols/adcp-extension.json",
+        "description": "AdCP protocol version and supported domains",
+        "params": {
+          "adcp_version": "2.5.0",
+          "protocols_supported": ["media_buy"]
+        }
+      }
+    ]
+  }
+}
+```
+
+This extension declares:
+- **adcp_version**: The AdCP specification version implemented by this agent (currently "2.5.0")
+- **protocols_supported**: Which AdCP protocol domains are supported (currently only "media_buy")
+
 ### Skill Invocation Patterns (AdCP PR #48)
 
 The server supports two invocation patterns for maximum flexibility:

src/a2a_server/adcp_a2a_server.py

@@ -30,6 +30,7 @@
 from a2a.server.request_handlers.request_handler import RequestHandler
 from a2a.types import (
     AgentCard,
+    AgentExtension,
     Artifact,
     DataPart,
     InternalError,
@@ -2200,14 +2201,31 @@ def create_agent_card() -> AgentCard:
     server_url = get_a2a_server_url()
 
     from a2a.types import AgentCapabilities, AgentSkill
+    from adcp import get_adcp_version
+
+    # Create AdCP extension (AdCP 2.5 spec)
+    # As of adcp 2.12.1, get_adcp_version() returns the protocol version (e.g., "2.5.0")
+    # Previously it returned the schema version (e.g., "v1"), but this was fixed upstream
+    protocol_version = get_adcp_version()
+    adcp_extension = AgentExtension(
+        uri=f"https://adcontextprotocol.org/schemas/{protocol_version}/protocols/adcp-extension.json",
+        description="AdCP protocol version and supported domains",
+        params={
+            "adcp_version": protocol_version,
+            "protocols_supported": ["media_buy"],  # Only media_buy protocol is currently supported
+        },
+    )
 
     # Create the agent card with minimal required fields
     agent_card = AgentCard(
         name="AdCP Sales Agent",
         description="AI agent for programmatic advertising campaigns via AdCP protocol",
         version="1.0.0",
         protocol_version="1.0",
-        capabilities=AgentCapabilities(push_notifications=True),
+        capabilities=AgentCapabilities(
+            push_notifications=True,
+            extensions=[adcp_extension],
+        ),
         default_input_modes=["message"],
         default_output_modes=["message"],
         skills=[

tests/e2e/test_a2a_endpoints_working.py

@@ -55,6 +55,24 @@ def test_well_known_agent_json_endpoint_live(self):
                 # Note: A2A spec uses security/securitySchemes instead of simple authentication field
                 assert "security" in data or "securitySchemes" in data
 
+                # AdCP 2.5: Should have AdCP extension in capabilities
+                assert "capabilities" in data
+                assert "extensions" in data["capabilities"]
+                extensions = data["capabilities"]["extensions"]
+                assert isinstance(extensions, list)
+                assert len(extensions) > 0
+
+                # Find AdCP extension
+                adcp_ext = None
+                for ext in extensions:
+                    if "adcp-extension" in ext.get("uri", ""):
+                        adcp_ext = ext
+                        break
+
+                assert adcp_ext is not None, "AdCP extension not found in live agent card"
+                assert adcp_ext["params"]["adcp_version"] == "2.5.0"
+                assert "media_buy" in adcp_ext["params"]["protocols_supported"]
+
         except (requests.ConnectionError, requests.Timeout):
             pytest.skip("A2A server not running on localhost:8091")
 
@@ -157,6 +175,43 @@ def test_create_agent_card_function(self):
             assert hasattr(skill, "name")
             assert hasattr(skill, "description")
 
+    def test_agent_card_adcp_extension(self):
+        """Test that agent card includes AdCP 2.5 extension."""
+        from src.a2a_server.adcp_a2a_server import create_agent_card
+
+        agent_card = create_agent_card()
+
+        # Check capabilities has extensions
+        assert hasattr(agent_card, "capabilities")
+        assert agent_card.capabilities is not None
+        assert hasattr(agent_card.capabilities, "extensions")
+        assert agent_card.capabilities.extensions is not None
+        assert len(agent_card.capabilities.extensions) > 0
+
+        # Find AdCP extension
+        adcp_ext = None
+        for ext in agent_card.capabilities.extensions:
+            if "adcp-extension" in ext.uri:
+                adcp_ext = ext
+                break
+
+        assert adcp_ext is not None, "AdCP extension not found in capabilities.extensions"
+
+        # Validate AdCP extension structure
+        assert adcp_ext.uri == "https://adcontextprotocol.org/schemas/2.5.0/protocols/adcp-extension.json"
+        assert adcp_ext.params is not None
+        assert "adcp_version" in adcp_ext.params
+        assert "protocols_supported" in adcp_ext.params
+
+        # Validate AdCP extension values
+        assert adcp_ext.params["adcp_version"] == "2.5.0"
+        protocols = adcp_ext.params["protocols_supported"]
+        assert isinstance(protocols, list)
+        assert len(protocols) >= 1
+        # Currently only media_buy protocol is supported
+        assert "media_buy" in protocols
+        assert set(protocols) == {"media_buy"}, "Only media_buy protocol is currently supported"
+
     def test_agent_card_skills_coverage(self):
         """Test that agent card includes expected AdCP skills."""
         from src.a2a_server.adcp_a2a_server import create_agent_card