refactor: reorder toolbox creation logic and add default tools test

- Move toolbox creation before tool validation to enable default toolbox usage
- Add test for loading tools from default toolbox without explicit toolbox parameter
- Mock strands_tools dependencies in tests to avoid external dependencies
- Verify that file_read tool can be loaded from default configuration

🤖 Assisted by Amazon Q Developer

Author: mrlee-amazon

src/strands/experimental/agent_config.py

@@ -67,18 +67,16 @@ def __init__(self, config_source: str | dict[str, any], tool_box: ToolBox | None
         self.system_prompt = config_data.get('prompt')  # Only accept 'prompt' key
         self._raise_exception_on_missing_tool = raise_exception_on_missing_tool
 
-        # Process tools configuration if provided
-        config_tools = config_data.get('tools')
-        if config_tools is not None and tool_box is None:
-            raise ValueError("Tool names specified in config but no ToolBox provided")
-        
         # Handle tool selection from ToolBox
         if tool_box is not None:
             self._toolbox = tool_box
         else:
             # Create default ToolBox with strands_tools
             self._toolbox = self._create_default_toolbox()
 
+        # Process tools configuration if provided
+        config_tools = config_data.get('tools')
+        
         # Track configured tools separately from full tool pool
         self._configured_tools = []
 

tests/strands/experimental/test_agent_config.py

@@ -158,12 +158,23 @@ def test_agent_config_tool_validation_error(self):
             }, tool_box=toolbox)
 
     def test_agent_config_tools_without_toolbox_error(self):
-        """Test that specifying tools without ToolBox raises error."""
-        with pytest.raises(ValueError, match="Tool names specified in config but no ToolBox provided"):
-            AgentConfig({
+        """Test that config can load tools from default toolbox when strands_tools is available."""
+        import unittest.mock
+        from strands.experimental.tool_box import ToolBox
+        
+        # Create a mock toolbox with the tools we want
+        mock_toolbox = ToolBox()
+        mock_file_read = self.MockTool("file_read")
+        mock_toolbox.add_tool(mock_file_read)
+        
+        # Patch the _create_default_toolbox method to return our mock
+        with unittest.mock.patch.object(AgentConfig, '_create_default_toolbox', return_value=mock_toolbox):
+            config = AgentConfig({
                 "model": "test-model",
-                "tools": ["calculator"]
+                "tools": ["file_read"]
             })
+            assert len(config.configured_tools) == 1
+            assert config.configured_tools[0].tool_name == "file_read"
 
     def test_agent_config_no_strands_tools_error(self):
         """Test that missing strands_tools without ToolBox raises ImportError."""
@@ -208,3 +219,23 @@ def test_agent_config_missing_tool_validation_with_flag_true(self):
                 "model": "test-model",
                 "tools": ["missing_tool"]
             }, tool_box=custom_toolbox, raise_exception_on_missing_tool=True)
+
+    def test_agent_config_loads_from_default_tools_without_toolbox(self):
+        """Test that config can load tools from default strands_tools without explicit toolbox."""
+        import unittest.mock
+        from strands.experimental.tool_box import ToolBox
+        
+        # Create a mock toolbox with the tools we want
+        mock_toolbox = ToolBox()
+        mock_file_read = self.MockTool("file_read")
+        mock_toolbox.add_tool(mock_file_read)
+        
+        # Patch the _create_default_toolbox method to return our mock
+        with unittest.mock.patch.object(AgentConfig, '_create_default_toolbox', return_value=mock_toolbox):
+            config = AgentConfig({
+                "model": "test-model", 
+                "tools": ["file_read"]
+            })
+            # Verify the tool was loaded from the default toolbox
+            assert len(config.configured_tools) == 1
+            assert config.configured_tools[0].tool_name == "file_read"