You can develop custom code outside D365 F&SCM to directly run a custom service that is provided for Connectivity Studio web services.
To use the external custom code to run a:
SOAP-based custom service, use this URL:
https://Instancename.cloudax.dynamics.com/soap/services/BisWsWebserviceOperation?wsdl
JSON-based custom service, use one of these URLS:
https://Instancename.cloudax.dynamics.com/api/services/BisWsWebserviceOperation/BisWsWebserviceCall/executeOperation. This is the basic URL.
https://Instancename.cloudax.dynamics.com/api/services/BisWsWebserviceOperation/BisWsWebserviceCall/executeOperationV2. Use this URL if you want to run the web service for a specific company. The 'companyId' parameter in the body parameters is only applicable if you use this URL. Make sure the D365 F&SCM user has permission to access the specified company.