GPTs don’t come with an API, there is the assistant API, but it is a bit different and quite expensive
You are able to upload all the docs directly to a persona, but fundamentally you will not be able to offload costs to users like you can for GPTs, so you will be on the hook for usage, if that is acceptable there are 2 alternatives
- Upload the docs to a persona
- Or, create the documents on Discourse and lean on the search tool