# 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:
@abstractmethods: These methods must be implemented by subclasses.@virtualmethods: 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" %}