Frequently-used tools can be started from the Startup directory; but if rarely used, start them by dragging into the scene.
If all tools in the startup directory are created like SafeToolCreationExample.py, you have the best of both worlds: a tool is executed once and can be dragged and dropped in the viewer when needed.
Rather than using FBTool, you should use pyfbsdk_additions::CreateUniqueTool or pyfbsdk_additions::CreateTool which ensure that the tools are added to the tool list and that the Python ToolManager knows about them.
Unlike FBTool, CreateUniqueTool and CreateTool use the Python ToolManager.
Not recommended, as it does not register your tool with the Python ToolManager.