Download a STEP file of the tool you want to define in Mastercam and place it in a known location.
In your Mastercam file open the Tool Manager found in the Toolpaths tab.
In the right click context menu select Create tool
Select Custom tool and click Next
Click the Import custom geometry from a file icon then click Next
Select the download file and click Open
Define the tool properties and click Finish
Select the Green Check to exit the Tool Manager
Select your custom tool in the toolpath parameters – the tool will load as it was defined
Backplot the toolpath – The custom tool will be displayed as shown