fix(a2a): Support instruction providers in cards

src/google/adk/a2a/utils/agent_card_builder.py

@@ -350,20 +350,20 @@ def _build_agent_description(agent: BaseNode) -> str:
 
 
 def _build_llm_agent_description_with_instructions(agent: LlmAgent) -> str:
-  """Build agent description including instructions for LlmAgents."""
+  """Build agent description including static instructions for LlmAgents."""
   description_parts = []
 
   # Add agent description
   if agent.description:
     description_parts.append(agent.description)
 
-  # Add instruction (with pronoun replacement) - only for LlmAgent
-  if agent.instruction:
+  # Instruction providers require runtime context, which is unavailable while
+  # building a static agent card.
+  if isinstance(agent.instruction, str) and agent.instruction:
     instruction = _replace_pronouns(agent.instruction)
     description_parts.append(instruction)
 
-  # Add global instruction (with pronoun replacement) - only for LlmAgent
-  if agent.global_instruction:
+  if isinstance(agent.global_instruction, str) and agent.global_instruction:
     global_instruction = _replace_pronouns(agent.global_instruction)
     description_parts.append(global_instruction)
 
@@ -551,8 +551,9 @@ async def _extract_examples_from_agent(
   except Exception as e:
     logger.warning('Failed to extract examples from tools: %s', e)
 
-  # If no example_tool found, try to extract examples from instruction
-  if agent.instruction:
+  # Dynamic instructions need runtime context and cannot provide static
+  # examples for an agent card.
+  if isinstance(agent.instruction, str) and agent.instruction:
     return _extract_examples_from_instruction(agent.instruction)
 
   return None

tests/unittests/a2a/utils/test_agent_card_builder.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from unittest.mock import AsyncMock
 from unittest.mock import Mock
 from unittest.mock import patch
 
@@ -322,6 +323,56 @@ async def test_build_succeeds_for_llm_agent(self):
     skill_ids = [skill.id for skill in card.skills]
     assert "writer" in skill_ids
 
+  async def test_build_omits_sync_instruction_provider(self):
+    """A static card omits a sync instruction that needs runtime context."""
+    instruction_provider = Mock(return_value="You use runtime context.")
+    agent = LlmAgent(
+        name="provider_agent",
+        description="Uses runtime instructions.",
+        instruction=instruction_provider,
+    )
+
+    card = await AgentCardBuilder(agent=agent).build()
+
+    assert card.skills[0].description == "Uses runtime instructions."
+    instruction_provider.assert_not_called()
+
+  async def test_build_omits_async_instruction_provider(self):
+    """A static card omits an async instruction that needs runtime context."""
+    instruction_provider = AsyncMock(
+        return_value="You use async runtime context."
+    )
+    agent = LlmAgent(
+        name="async_provider_agent",
+        description="Uses async runtime instructions.",
+        instruction=instruction_provider,
+    )
+
+    card = await AgentCardBuilder(agent=agent).build()
+
+    assert card.skills[0].description == "Uses async runtime instructions."
+    instruction_provider.assert_not_called()
+
+  async def test_build_omits_global_instruction_provider(self):
+    """A static card omits a global instruction that needs runtime context."""
+    global_instruction_provider = Mock(
+        return_value="You use global runtime context."
+    )
+    agent = LlmAgent(
+        name="global_provider_agent",
+        description="Answers questions.",
+        instruction="You answer user questions.",
+        global_instruction=global_instruction_provider,
+    )
+
+    card = await AgentCardBuilder(agent=agent).build()
+
+    assert (
+        card.skills[0].description
+        == "Answers questions. I answer user questions."
+    )
+    global_instruction_provider.assert_not_called()
+
   async def test_build_succeeds_for_workflow_with_llm_agent_node(self):
     """AgentCardBuilder.build succeeds for a Workflow (no sub_agents)."""
     writer = LlmAgent(