# Tool Types
In order to make development of new Tools quick, easy and relatively boilerplate-free, all Tools extend
one of three base classes, which provide the functionality required to integrate seamlessly into the Cornerstone Tools framework.
Base classes have two types of methods of interest to Tool developers:
@abstract
methods: These methods must be implemented by subclasses.@virtual
methods: These methods have default functionality, but may be overridden by subclasses to alter functionality.
Check the api
docs (opens new window) for full documentation of the api.
{% include "./base-tool.md" %}
{% include "./base-annotation-tool.md" %}
{% include "./base-brush-tool.md" %}
{% include "./base-segmentation-tool.md" %}