How can I read attributes from a json stored using FME Server Automation writer ?

Hello,

I store attributes of my workspace in an json array (JSON_FILE_PARAM) using the FME Server Automations Writer (myWriter).

{"automation.id":"c48fb4a8-5757-4207-867c-6d0de3947b5e","email.subject":"mySubject","email.received":"Wed Sep 13 09:37:26 CEST 2023","email.body":"e-mail:myEmail@provider.com"}

Now, in my automation, I'd like to use the attributes as user keys:

{route.myWriter.JSON_FILE_PARAM.email.body}

I do have access to those attributes stored OUTSIDE the list but not INSIDE.

I'm using FME Flow version 2020.