So you stood up a REST driver so you can use it as an endpoint to manage users?  Probably better to use the IDApps REST API since it is meant for that and hopefully better written.

Having a remove-all-values after a add-value means it will clear the attribute in the IDV.  So why is the JSON being interpreted that way?  Can you show us the <driver-operation-data> incoming before it is converted to XML.

What I did was to create a simple WebAPI which then the REST driver consume data from.

I am misunderstanding.  Which channel is this happening on?   An event on the Sub channel, or a poll/query on the Pub channel?

This is happening in a poll on the Pub channel

See https://community.microfocus.com/cyberres/iga/idm/f/discussions/296101/help-with-parsing-rest-json-response-to-xds/304332

You are generating a modify for user that is already associated. Do you really have a user that already has an association for Rest Driver with a value of "ktrötter"?

If not, you should be creating an add and have the matching policy and merge processor handle this.

Thanks!

You´re right I don´t have a user that already has an association for Rest Driver with that value, for some reason my driver sees it as a modify which probably is the issue here.

Your driver sees it as a modify, since it probably is.  If there were an association (Which the shim is required to provide) then it would go properly through synthetic add/match/merge process.  So I would work on getting the association set.

Thanks for the tip. Tried that solution but the result I got is: number of responses: 1 when I am executing the script.

Found this solution which solved it: (+) REST Driver Converting response JSON to Instance - Identity Manager User Discussions - OpenText NetIQ Identity Manager (microfocus.com)