How to get fax-log-id for faxviewer by api?

HI.
there is api for fax files.

how to get {{fax_log_id}}, when fax imcoming.
http://{{host}}/api/v2/virtual_faxes/log/{{fax_log_id}}

we want to get fax files by external app or web.

let me know some hints
thanks