Hello Kai,
do you mean the URL for Inbound API?
http://help.sap.com/saphelp_byd1508/en/PUBLISHING/PSM_ISI_R_II_MANAGE_PRODUCT_DESIGN_IN.html
The List of all API ist avaiable here:
http://help.sap.com/saphelp_byd1508/en/PUBLISHING/IntegrationServices.html
Best Regard,
Hendrik