feat(tools): Add an option to disallow propagating runner plugins to AgentTool runner

Merge https://github.com/google/adk-python/pull/2779

Fixes #2780

### testing plan
not available as is doesn't introduce new functionality

Co-authored-by: Wei Sun (Jack) <weisun@google.com>
COPYBARA_INTEGRATE_REVIEW=https://github.com/google/adk-python/pull/2779 from davidkl97:feature/agent-tool-plugins a602c808789f3daeed6244e352a6fb8fb6972de3
PiperOrigin-RevId: 835366974

src/google/adk/tools/agent_tool.py

@@ -45,11 +45,22 @@ class AgentTool(BaseTool):
   Attributes:
     agent: The agent to wrap.
     skip_summarization: Whether to skip summarization of the agent output.
+    include_plugins: Whether to propagate plugins from the parent runner context
+      to the agent's runner. When True (default), the agent will inherit all
+      plugins from its parent. Set to False to run the agent with an isolated
+      plugin environment.
   """
 
-  def __init__(self, agent: BaseAgent, skip_summarization: bool = False):
+  def __init__(
+      self,
+      agent: BaseAgent,
+      skip_summarization: bool = False,
+      *,
+      include_plugins: bool = True,
+  ):
     self.agent = agent
     self.skip_summarization: bool = skip_summarization
+    self.include_plugins = include_plugins
 
     super().__init__(name=agent.name, description=agent.description)
 
@@ -130,6 +141,11 @@ class AgentTool(BaseTool):
         invocation_context.app_name if invocation_context else None
     )
     child_app_name = parent_app_name or self.agent.name
+    plugins = (
+        tool_context._invocation_context.plugin_manager.plugins
+        if self.include_plugins
+        else None
+    )
     runner = Runner(
         app_name=child_app_name,
         agent=self.agent,
@@ -137,7 +153,7 @@ class AgentTool(BaseTool):
         session_service=InMemorySessionService(),
         memory_service=InMemoryMemoryService(),
         credential_service=tool_context._invocation_context.credential_service,
-        plugins=list(tool_context._invocation_context.plugin_manager.plugins),
+        plugins=plugins,
     )
 
     state_dict = {
@@ -192,7 +208,9 @@ class AgentTool(BaseTool):
         agent_tool_config.agent, config_abs_path
     )
     return cls(
-        agent=agent, skip_summarization=agent_tool_config.skip_summarization
+        agent=agent,
+        skip_summarization=agent_tool_config.skip_summarization,
+        include_plugins=agent_tool_config.include_plugins,
     )
 
 
@@ -204,3 +222,6 @@ class AgentToolConfig(BaseToolConfig):
 
   skip_summarization: bool = False
   """Whether to skip summarization of the agent output."""
+
+  include_plugins: bool = True
+  """Whether to include plugins from parent runner context."""

tests/unittests/tools/test_agent_tool.py

@@ -570,3 +570,112 @@ def test_agent_tool_response_schema_with_input_schema_no_output_vertex_ai(
   # Should have string response schema for VERTEX_AI when no output_schema
   assert declaration.response is not None
   assert declaration.response.type == types.Type.STRING
+
+
+def test_include_plugins_default_true():
+  """Test that plugins are propagated by default (include_plugins=True)."""
+
+  # Create a test plugin that tracks callbacks
+  class TrackingPlugin(BasePlugin):
+
+    def __init__(self, name: str):
+      super().__init__(name)
+      self.before_agent_calls = 0
+
+    async def before_agent_callback(self, **kwargs):
+      self.before_agent_calls += 1
+
+  tracking_plugin = TrackingPlugin(name='tracking')
+
+  mock_model = testing_utils.MockModel.create(
+      responses=[function_call_no_schema, 'response1', 'response2']
+  )
+
+  tool_agent = Agent(
+      name='tool_agent',
+      model=mock_model,
+  )
+
+  root_agent = Agent(
+      name='root_agent',
+      model=mock_model,
+      tools=[AgentTool(agent=tool_agent)],  # Default include_plugins=True
+  )
+
+  runner = testing_utils.InMemoryRunner(root_agent, plugins=[tracking_plugin])
+  runner.run('test1')
+
+  # Plugin should be called for both root_agent and tool_agent
+  assert tracking_plugin.before_agent_calls == 2
+
+
+def test_include_plugins_explicit_true():
+  """Test that plugins are propagated when include_plugins=True."""
+
+  class TrackingPlugin(BasePlugin):
+
+    def __init__(self, name: str):
+      super().__init__(name)
+      self.before_agent_calls = 0
+
+    async def before_agent_callback(self, **kwargs):
+      self.before_agent_calls += 1
+
+  tracking_plugin = TrackingPlugin(name='tracking')
+
+  mock_model = testing_utils.MockModel.create(
+      responses=[function_call_no_schema, 'response1', 'response2']
+  )
+
+  tool_agent = Agent(
+      name='tool_agent',
+      model=mock_model,
+  )
+
+  root_agent = Agent(
+      name='root_agent',
+      model=mock_model,
+      tools=[AgentTool(agent=tool_agent, include_plugins=True)],
+  )
+
+  runner = testing_utils.InMemoryRunner(root_agent, plugins=[tracking_plugin])
+  runner.run('test1')
+
+  # Plugin should be called for both root_agent and tool_agent
+  assert tracking_plugin.before_agent_calls == 2
+
+
+def test_include_plugins_false():
+  """Test that plugins are NOT propagated when include_plugins=False."""
+
+  class TrackingPlugin(BasePlugin):
+
+    def __init__(self, name: str):
+      super().__init__(name)
+      self.before_agent_calls = 0
+
+    async def before_agent_callback(self, **kwargs):
+      self.before_agent_calls += 1
+
+  tracking_plugin = TrackingPlugin(name='tracking')
+
+  mock_model = testing_utils.MockModel.create(
+      responses=[function_call_no_schema, 'response1', 'response2']
+  )
+
+  tool_agent = Agent(
+      name='tool_agent',
+      model=mock_model,
+  )
+
+  root_agent = Agent(
+      name='root_agent',
+      model=mock_model,
+      tools=[AgentTool(agent=tool_agent, include_plugins=False)],
+  )
+
+  runner = testing_utils.InMemoryRunner(root_agent, plugins=[tracking_plugin])
+  runner.run('test1')
+
+  # Plugin should only be called for root_agent, not tool_agent
+  assert tracking_plugin.before_agent_calls == 1