1. A method for extensible context based user interface simplification for a model driven development tool, the method comprising: executing the model driven development tool in a memory of a host computer, the tool comprising a multiplicity of user interface components including tool items and also model components of a model loaded for processing in the tool; registering different ones of the tool items in a tool item registry in association with corresponding contexts of the model driven development tool; detecting a context of the contexts change to a new context in the model driven development tool based upon a selection of a new one of the model components in the model driven development tool, wherein dectecting the context change to the new context in the model driven development tool comprises detecting the selection of the new model component associated with a context object in the model driven development tool, the context object providing the new context; locating ones of the tool items in the registry mapped to the new context; and, displaying the located tool items in the model driven development tool.