You can use a functional testing tool, such as SoapUI, to view SOAP API input and output parameters.
Create a SOAP project and import the WSDL file into the project. The operations you can perform using the business entity services appear as nodes in SoapUI. Each operation has a request and a response message format. SoapUI creates a sample request for each operation when you import the WSDL file.
Open the project and double-click a request to open the request editor. The following image shows the input parameters in SoapUI for the WritePerson SOAP API: