fix: Cache BaseToolset.get_tools() for calls within the same invocation

src/google/adk/tools/base_toolset.py

@@ -80,6 +80,8 @@ def __init__(
     """
     self.tool_filter = tool_filter
     self.tool_name_prefix = tool_name_prefix
+    self._cached_invocation_id: Optional[str] = None
+    self._cached_prefixed_tools: Optional[list[BaseTool]] = None
 
   @abstractmethod
   async def get_tools(
@@ -112,9 +114,19 @@ async def get_tools_with_prefix(
     Returns:
       list[BaseTool]: A list of tools with prefixed names if tool_name_prefix is provided.
     """
+    invocation_id = readonly_context.invocation_id if readonly_context else None
+
+    if (
+        self._cached_prefixed_tools is not None
+        and self._cached_invocation_id == invocation_id
+    ):
+      return self._cached_prefixed_tools
+
     tools = await self.get_tools(readonly_context)
 
     if not self.tool_name_prefix:
+      self._cached_invocation_id = invocation_id
+      self._cached_prefixed_tools = tools
       return tools
 
     prefix = self.tool_name_prefix
@@ -147,6 +159,8 @@ def _get_prefixed_declaration():
       tool_copy._get_declaration = _create_prefixed_declaration()
       prefixed_tools.append(tool_copy)
 
+    self._cached_invocation_id = invocation_id
+    self._cached_prefixed_tools = prefixed_tools
     return prefixed_tools
 
   async def close(self) -> None:

tests/unittests/tools/test_base_toolset.py

@@ -383,6 +383,58 @@ async def test_no_duplicate_prefixing():
   original_tools = await toolset.get_tools()
   assert original_tools[0].name == 'original'
 
-  # The prefixed tools should be different instances
-  assert prefixed_tools_1[0] is not prefixed_tools_2[0]
+  # The prefixed tools should be the same instance when cached
+  assert prefixed_tools_1[0] is prefixed_tools_2[0]
   assert prefixed_tools_1[0] is not original_tools[0]
+
+
+@pytest.mark.asyncio
+async def test_get_tools_with_prefix_caching():
+  """Test that get_tools_with_prefix caches results within the same invocation."""
+  tool1 = _TestingTool(name='tool1', description='Test tool 1')
+  toolset = _TestingToolset(tools=[tool1], tool_name_prefix='test')
+
+  session_service = InMemorySessionService()
+  session = await session_service.create_session(
+      app_name='test_app', user_id='test_user'
+  )
+  agent = SequentialAgent(name='test_agent')
+  invocation_context1 = InvocationContext(
+      invocation_id='inv-1',
+      agent=agent,
+      session=session,
+      session_service=session_service,
+  )
+  readonly_context1 = ReadonlyContext(invocation_context1)
+
+  # First call
+  tools1 = await toolset.get_tools_with_prefix(
+      readonly_context=readonly_context1
+  )
+  assert len(tools1) == 1
+  assert tools1[0].name == 'test_tool1'
+
+  # Second call with same context/invocation_id
+  tools2 = await toolset.get_tools_with_prefix(
+      readonly_context=readonly_context1
+  )
+  assert len(tools2) == 1
+  assert (
+      tools2 is tools1
+  )  # Should return the exact same list instance (from cache)
+
+  # Third call with different invocation_id
+  invocation_context2 = InvocationContext(
+      invocation_id='inv-2',
+      agent=agent,
+      session=session,
+      session_service=session_service,
+  )
+  readonly_context2 = ReadonlyContext(invocation_context2)
+
+  tools3 = await toolset.get_tools_with_prefix(
+      readonly_context=readonly_context2
+  )
+  assert len(tools3) == 1
+  assert tools3 is not tools1  # Should be a new list instance
+  assert tools3[0].name == 'test_tool1'