fix(agent_tool): ensure text output when skip_summarization is True

src/google/adk/flows/llm_flows/functions.py

@@ -21,6 +21,7 @@
 import copy
 import functools
 import inspect
+import json
 import logging
 import threading
 from typing import Any
@@ -962,6 +963,17 @@ def __build_response_event(
       parts=[part_function_response],
   )
 
+  if tool_context.actions.skip_summarization:
+    # When summarization is skipped, ensure a displayable text part is added.
+    if isinstance(function_result.get('result'), str):
+      result_text = function_result['result']
+    else:
+      # Safely serialize non-string results to JSON for display.
+      result_text = json.dumps(
+          function_result.get('result', function_result), ensure_ascii=False, default=str
+      )
+    content.parts.append(types.Part.from_text(text=result_text))
+
   function_response_event = Event(
       invocation_id=invocation_context.invocation_id,
       author=invocation_context.agent.name,

tests/unittests/tools/test_agent_tool.py

@@ -1164,3 +1164,113 @@ def test_empty_sequential_agent_falls_back_to_request(self):
 
     # Should fall back to 'request' parameter
     assert declaration.parameters.properties['request'].type == 'STRING'
+
+
+def test_agent_tool_skip_summarization_has_text_output():
+  """Tests that when skip_summarization is True, the final event contains text content."""
+
+  tool_agent_model = testing_utils.MockModel.create(responses=["tool_response_text"])
+  tool_agent = Agent(
+      name="tool_agent",
+      model=tool_agent_model,
+  )
+
+  agent_tool = AgentTool(agent=tool_agent, skip_summarization=True)
+
+  root_agent_model = testing_utils.MockModel.create(
+      responses=[
+          function_call_no_schema,
+          "final_summary_text_that_should_not_be_reached",
+      ]
+  )
+
+  root_agent = Agent(
+      name="root_agent",
+      model=root_agent_model,
+      tools=[agent_tool],
+  )
+
+  runner = testing_utils.InMemoryRunner(root_agent)
+  events = runner.run("start")
+
+  final_events = [e for e in events if e.is_final_response()]
+  assert final_events
+  last_event = final_events[-1]
+  assert last_event.is_final_response()
+
+  assert any(p.function_response for p in last_event.content.parts)
+
+  assert [p.text for p in last_event.content.parts if p.text] == ["tool_response_text"]
+
+
+def test_agent_tool_skip_summarization_preserves_json_string_output():
+  """Tests that structured output string is preserved as text when skipping summarization."""
+
+  tool_agent_model = testing_utils.MockModel.create(responses=['{"field": "value"}'])
+  tool_agent = Agent(
+      name="tool_agent",
+      model=tool_agent_model,
+  )
+
+  agent_tool = AgentTool(agent=tool_agent, skip_summarization=True)
+
+  root_agent_model = testing_utils.MockModel.create(
+      responses=[function_call_no_schema]
+  )
+
+  root_agent = Agent(
+      name="root_agent",
+      model=root_agent_model,
+      tools=[agent_tool],
+  )
+
+  runner = testing_utils.InMemoryRunner(root_agent)
+  events = runner.run("start")
+
+  final_events = [e for e in events if e.is_final_response()]
+  assert final_events
+  last_event = final_events[-1]
+  assert last_event.is_final_response()
+
+  text_parts = [p.text for p in last_event.content.parts if p.text]
+  assert text_parts
+
+  # Check that the JSON string content is preserved exactly
+  assert text_parts == ['{"field": "value"}']
+
+
+def test_agent_tool_skip_summarization_handles_non_string_result():
+  """Tests that non-string (dict) output is correctly serialized as JSON text."""
+
+  class CustomOutput(BaseModel):
+      value: int
+
+  tool_agent_model = testing_utils.MockModel.create(responses=['{"value": 123}'])
+  tool_agent = Agent(
+      name="tool_agent",
+      model=tool_agent_model,
+      output_schema=CustomOutput
+  )
+
+  agent_tool = AgentTool(agent=tool_agent, skip_summarization=True)
+
+  root_agent_model = testing_utils.MockModel.create(
+      responses=[function_call_no_schema]
+  )
+
+  root_agent = Agent(
+      name="root_agent",
+      model=root_agent_model,
+      tools=[agent_tool],
+  )
+
+  runner = testing_utils.InMemoryRunner(root_agent)
+  events = runner.run("start")
+
+  final_events = [e for e in events if e.is_final_response()]
+  assert final_events
+  last_event = final_events[-1]
+
+  text_parts = [p.text for p in last_event.content.parts if p.text]
+
+  assert text_parts == ['{"value": 123}']