We have no idea behind the underlying mechanics with the retrieval process. Yes, there’s a limit and yes for whatever reason it seems like OpenAI prefers you to send massive files instead of splitting them.
Generalized to typical RAG:
- Images are ignored
- PDF is not ideal as it’s meant more for printing and can do weird things to formatting
- Markdown may be best as it’s clean and the formatting is explicit
For anything serious I wouldn’t recommend using retrieval. As an example, I uploaded a single car care guide for a specific model. My Custom GPT gave me incorrect torque values that, if followed, would have led to my brake caliper & tires dismantling on the road.
If you are serious I would recommend using your own RAG system and either jumping into the API, or use Actions to make calls to it. You can use Actions with the RAG process by calling specific areas of dentistry, for example and shape the query