We have made an subroutine and mark this as an API (OData). This subroutine works fine when you use no parameters. When we profile with sql server the call is done but the parameter is null. We use the http call in the example but not sure this is correct.
HTTP call
http://web04/indicium/iam/100/fnc_getUserEmail?param_usr_id='itpartner\ronald'
Metadata
<Function Name="fnc_getUserEmail">
<Parameter Name="param_usr_id" Type="Edm.String"/>
<ReturnType Type="CENTER.subroutineScalarResult" Nullable="false"/>
</Function>