refactor: improve AgentConfig file handling and default tools

- Add static FILE_PREFIX constant for better file:// handling
- Use removeprefix() instead of substring indexing for cleaner code
- Add static DEFAULT_TOOLS list with experimental minimum viable tools
- Add comprehensive error handling for missing strands_tools
- Require either strands_tools installation or custom ToolPool
- Fix logic to check for tools before creating default ToolPool
- Update all tests to handle new validation requirements
- Add test for ImportError when strands_tools not available

🤖 Assisted by Amazon Q Developer

Author: mrlee-amazon

src/strands/experimental/agent_config.py

@@ -3,13 +3,20 @@
 """Experimental agent configuration with enhanced instantiation patterns."""
 
 import json
+import importlib
 
 from .tool_pool import ToolPool
 
+# Minimum viable list of tools to enable agent building
+# This list is experimental and will be revisited as tools evolve
+DEFAULT_TOOLS = ["file_read", "editor", "http_request", "shell", "use_agent"]
+
 
 class AgentConfig:
     """Agent configuration with toAgent() method and ToolPool integration."""
 
+    FILE_PREFIX = "file://"
+    
     def __init__(self, config_source: str | dict[str, any], tool_pool: "ToolPool | None" = None):
         """Initialize AgentConfig from file path or dictionary.
         
@@ -19,11 +26,11 @@ def __init__(self, config_source: str | dict[str, any], tool_pool: "ToolPool | N
         """
         if isinstance(config_source, str):
             # Require file:// prefix for file paths
-            if not config_source.startswith('file://'):
-                raise ValueError("File paths must be prefixed with 'file://'")
+            if not config_source.startswith(self.FILE_PREFIX):
+                raise ValueError(f"File paths must be prefixed with '{self.FILE_PREFIX}'")
 
             # Remove file:// prefix and load from file
-            file_path = config_source[7:]  # Remove 'file://' prefix
+            file_path = config_source.removeprefix(self.FILE_PREFIX)
             with open(file_path, 'r') as f:
                 config_data = json.load(f)
         else:
@@ -33,18 +40,20 @@ def __init__(self, config_source: str | dict[str, any], tool_pool: "ToolPool | N
         self.model = config_data.get('model')
         self.system_prompt = config_data.get('prompt')  # Only accept 'prompt' key
 
+        # Process tools configuration if provided
+        config_tools = config_data.get('tools')
+        if config_tools is not None and tool_pool is None:
+            raise ValueError("Tool names specified in config but no ToolPool provided")
+        
         # Handle tool selection from ToolPool
         if tool_pool is not None:
             self._tool_pool = tool_pool
         else:
-            self._tool_pool = ToolPool()
+            # Create default ToolPool with strands_tools
+            self._tool_pool = self._create_default_tool_pool()
 
-        # Process tools configuration if provided
-        config_tools = config_data.get('tools')
+        # Apply tool selection if specified
         if config_tools is not None:
-            if tool_pool is None:
-                raise ValueError("Tool names specified in config but no ToolPool provided")
-            
             # Validate all tool names exist in the ToolPool
             available_tools = tool_pool.list_tool_names()
             for tool_name in config_tools:
@@ -60,6 +69,24 @@ def __init__(self, config_source: str | dict[str, any], tool_pool: "ToolPool | N
 
             self._tool_pool = selected_pool
 
+    def _create_default_tool_pool(self) -> ToolPool:
+        """Create default ToolPool with strands_tools."""
+        pool = ToolPool()
+        
+        for tool in DEFAULT_TOOLS:
+            try:
+                module_name = f"strands_tools.{tool}"
+                tool_module = importlib.import_module(module_name)
+                pool.add_tools_from_module(tool_module)
+            except ImportError:
+                raise ImportError(
+                    f"strands_tools is not available and no ToolPool was specified. "
+                    f"Either install strands_tools with 'pip install strands-agents-tools' "
+                    f"or provide your own ToolPool with native tools."
+                )
+        
+        return pool
+    
     @property
     def tool_pool(self) -> "ToolPool":
         """Get the tool pool for this configuration.

tests/strands/experimental/test_agent_config.py

@@ -15,7 +15,8 @@ class TestAgentConfig:
 
     def test_agent_config_creation(self):
         """Test AgentConfig can be created with dict config."""
-        config = AgentConfig({"model": "test-model"})
+        # Provide empty ToolPool since strands_tools not available in tests
+        config = AgentConfig({"model": "test-model"}, tool_pool=ToolPool())
         assert config.model == "test-model"
 
     def test_agent_config_with_tools(self):
@@ -24,7 +25,7 @@ def test_agent_config_with_tools(self):
         config = AgentConfig({
             "model": "test-model",
             "prompt": "Test prompt"
-        })
+        }, tool_pool=ToolPool())
 
         assert config.model == "test-model"
         assert config.system_prompt == "Test prompt"
@@ -47,7 +48,7 @@ def test_agent_config_file_prefix_valid(self):
             temp_path = f.name
 
         try:
-            config = AgentConfig(f"file://{temp_path}")
+            config = AgentConfig(f"file://{temp_path}", tool_pool=ToolPool())
             assert config.model == "test-model"
             assert config.system_prompt == "Test prompt"
         finally:
@@ -57,7 +58,7 @@ def test_agent_config_file_prefix_valid(self):
     def test_to_agent_method_exists(self):
         """Test that toAgent method exists and is callable."""
 
-        config = AgentConfig({"model": "test-model"})
+        config = AgentConfig({"model": "test-model"}, tool_pool=ToolPool())
         assert hasattr(config, 'toAgent')
         assert callable(config.toAgent)
 
@@ -68,7 +69,7 @@ def test_to_agent_calls_agent_constructor(self, mock_agent):
         config = AgentConfig({
             "model": "test-model",
             "prompt": "Test prompt"
-        })
+        }, tool_pool=ToolPool())
 
         config.toAgent()
 
@@ -81,15 +82,15 @@ def test_to_agent_calls_agent_constructor(self, mock_agent):
     def test_agent_config_has_tool_pool(self):
         """Test AgentConfig creates empty ToolPool by default."""
 
-        config = AgentConfig({"model": "test-model"})
+        config = AgentConfig({"model": "test-model"}, tool_pool=ToolPool())
         assert hasattr(config, 'tool_pool')
         assert config.tool_pool.list_tool_names() == []
 
     @patch('strands.agent.agent.Agent')
     def test_to_agent_with_empty_tool_pool(self, mock_agent):
         """Test that toAgent uses empty ToolPool by default."""
 
-        config = AgentConfig({"model": "test-model"})
+        config = AgentConfig({"model": "test-model"}, tool_pool=ToolPool())
         config.toAgent()
 
         # Should be called with empty tools list
@@ -102,7 +103,7 @@ def test_to_agent_with_empty_tool_pool(self, mock_agent):
     def test_to_agent_with_tool_pool_parameter(self, mock_agent):
         """Test that toAgent accepts ToolPool parameter."""
 
-        config = AgentConfig({"model": "test-model"})
+        config = AgentConfig({"model": "test-model"}, tool_pool=ToolPool())
         pool = ToolPool()
 
         config.toAgent(tools=pool)
@@ -187,3 +188,8 @@ def test_agent_config_tools_without_pool_error(self):
                 "model": "test-model",
                 "tools": ["calculator"]
             })
+    
+    def test_agent_config_no_strands_tools_error(self):
+        """Test that missing strands_tools without ToolPool raises ImportError."""
+        with pytest.raises(ImportError, match="strands_tools is not available and no ToolPool was specified"):
+            AgentConfig({"model": "test-model"})