Hi rkuechler,
The best way I've found to do this is setting on output variable as MimeAttachment. This will be expose in the API call as a Base64 string.
Now, be careful because this will be saved in the database so, if you are creating large files, this will have a big impact. I've done this to export a not so big CSV and JSON files.
An example:
1. Create a Json

2. Output the mimeAttachment

3. Api call response

Hope this helps.
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Damián Bacalov
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