[dc_rog]

In a python-based backend, one suggestion for retrieving "additional details" could be SMS via Twilio or other. Easy to use with Python and might be a good context fit for following up that doesn't require a user to be at their computer.

This also seems like a potential candidate for automating using some of the tools they might already have - forms, sheets, email. Forms has the ability to ask for additional info based on the previous answer (might fix the need to ask for more info).

You aren't generating an "invoice" but a work/spec sheet might follow a similar pattern. One of the first search results I found(no affiliation) https://howtogapps.com/generate-invoices-using-google-form-a...