It looks like the "sis-set-config" or "sis-set-config-async" APIs (using Ontapi 1.30 Vserver) would be in the ballpark of what you're looking for.
Here's the API output generated from ZEDI - hope that's helpful!
<?xml version="1.0" encoding="UTF-8"?>
<netapp xmlns="http://www.netapp.com/filer/admin" version="1.130">
<sis-set-config>
<enable-compression></enable-compression>
<enable-idd></enable-idd>
<enable-inline-compression></enable-inline-compression>
<path></path>
<policy-name></policy-name>
<quick-check-fsize></quick-check-fsize>
<schedule></schedule>
</sis-set-config>
</netapp>
Donny