Retrieval tool rules for an Assistant

I am a bit confused about the rules around the retrieval files.

You can associate file ids with an Assistant when the purpose is ‘assistant’. However, I can’t find out how to assign a file to the interpreter tool or the retrieval tool? I think it is impossible to keep those separate? The examples in the documentation use the same means to associate a file for both tools. What happens if you activate both tools with two files?

You can enable ‘retrieval’ on on the Assistant level and you can enable/disable it on the Run level, as well as that you can add files on both levels. How do those interact? Is it disabled when you do not add the ‘retrieval’ on the Run level? Does it still work when it is disabled on the Assistant level but enabled on the Run level?

What are the chunking rules in general?

Where can I see what the Assistant did? Which chunks did it find and apply?