fix: support both Pydantic and Protobuf AgentCard during A2aAgent serialization

PiperOrigin-RevId: 918921714

Author: vertex-sdk-bot

agentplatform/_genai/_agent_engines_utils.py

@@ -665,9 +665,17 @@ def _generate_class_methods_spec_or_raise(
             class_method = _to_proto(schema_dict)
             class_method[_MODE_KEY_IN_SCHEMA] = mode
             if hasattr(agent, "agent_card"):
-                class_method[_A2A_AGENT_CARD] = json_format.MessageToJson(
-                    getattr(agent, "agent_card")
-                )
+                card = getattr(agent, "agent_card")
+                if card is not None:
+                    if hasattr(card, "model_dump_json"):
+                        class_method[_A2A_AGENT_CARD] = card.model_dump_json()
+                    elif hasattr(card, "DESCRIPTOR"):
+                        class_method[_A2A_AGENT_CARD] = json_format.MessageToJson(card)
+                    else:
+                        raise TypeError(
+                            f"Unsupported AgentCard type: {type(card)}. "
+                            "Only Pydantic models and Protobuf Messages are supported."
+                        )
             class_methods_spec.append(class_method)
 
     return class_methods_spec

agentplatform/_genai/agent_engines.py

@@ -2498,13 +2498,23 @@ def _create_config(
 
             if hasattr(agent, "agent_card"):
                 agent_card = getattr(agent, "agent_card")
-                if agent_card:
+                if agent_card is not None:
                     try:
-                        from google.protobuf import json_format
-
-                        agent_engine_spec["agent_card"] = json_format.MessageToDict(
-                            agent_card
-                        )
+                        if hasattr(agent_card, "model_dump"):
+                            agent_engine_spec["agent_card"] = agent_card.model_dump(
+                                exclude_none=True
+                            )
+                        elif hasattr(agent_card, "DESCRIPTOR"):
+                            from google.protobuf import json_format
+
+                            agent_engine_spec["agent_card"] = json_format.MessageToDict(
+                                agent_card
+                            )
+                        else:
+                            raise TypeError(
+                                f"Unsupported AgentCard type: {type(agent_card)}. "
+                                "Only Pydantic models and Protobuf Messages are supported."
+                            )
                     except Exception as e:
                         raise ValueError(
                             f"Failed to convert agent card to dict (serialization error): {e}"

agentplatform/agent_engines/_agent_engines.py

@@ -2003,11 +2003,19 @@ def _generate_class_methods_spec_or_raise(
             class_method[_MODE_KEY_IN_SCHEMA] = mode
             # A2A agent card is a special case, when running in A2A mode,
             if hasattr(agent_engine, "agent_card"):
-                from google.protobuf import json_format
-
-                class_method[_A2A_AGENT_CARD] = json_format.MessageToJson(
-                    getattr(agent_engine, "agent_card")
-                )
+                card = getattr(agent_engine, "agent_card")
+                if card is not None:
+                    if hasattr(card, "model_dump_json"):
+                        class_method[_A2A_AGENT_CARD] = card.model_dump_json()
+                    elif hasattr(card, "DESCRIPTOR"):
+                        from google.protobuf import json_format
+
+                        class_method[_A2A_AGENT_CARD] = json_format.MessageToJson(card)
+                    else:
+                        raise TypeError(
+                            f"Unsupported AgentCard type: {type(card)}. "
+                            "Only Pydantic models and Protobuf Messages are supported."
+                        )
             class_methods_spec.append(class_method)
 
     return class_methods_spec