fix(a2a): adopt a directly supplied agent card's description

Co-authored-by: George Weale <gweale@google.com>
PiperOrigin-RevId: 961611760

src/google/adk/agents/remote_a2a_agent.py

@@ -248,6 +248,12 @@ class RemoteA2aAgent(BaseAgent):
     # Validate and store agent card reference
     if isinstance(agent_card, AgentCard):
       self._agent_card = agent_card
+      # Update description if empty. A card supplied directly never goes
+      # through the resolution path, so adopt it here instead; a parent agent
+      # reads the description to build its transfer instruction, which happens
+      # before this agent ever runs.
+      if not self.description and agent_card.description:
+        self.description = agent_card.description
     elif isinstance(agent_card, str):
       if not agent_card.strip():
         raise ValueError("agent_card string cannot be empty")

tests/unittests/agents/test_remote_a2a_agent.py

@@ -215,6 +215,26 @@ class TestRemoteA2aAgentInit:
     assert agent._httpx_client_needs_cleanup is True
     assert agent._is_resolved is False
 
+  def test_init_with_agent_card_object_adopts_card_description(self):
+    """Test description is autopopulated from a directly supplied card."""
+    agent_card = create_test_agent_card(description="Converts currencies")
+
+    agent = RemoteA2aAgent(name="test_agent", agent_card=agent_card)
+
+    assert agent.description == "Converts currencies"
+
+  def test_init_with_agent_card_object_keeps_explicit_description(self):
+    """Test an explicit description wins over the card's."""
+    agent_card = create_test_agent_card(description="Converts currencies")
+
+    agent = RemoteA2aAgent(
+        name="test_agent",
+        agent_card=agent_card,
+        description="Test description",
+    )
+
+    assert agent.description == "Test description"
+
   def test_init_with_url_string(self):
     """Test initialization with URL string."""
     agent = RemoteA2aAgent(