Cloudflare workers fetch api default headers

We have a Cloudflare worker which intercepts the request fetches data from a couple of different endpoints (does some business and caching logic) and serves response.
I have been wondering are there some docs on fetch api (specific for cf workers).
To be more specific which headers fetch api adds by default?

I believe none except for the host header and the minimum set to make the request.

@matteo don’t they need to add at least cf-headers the ones used for circuit breaking, to prevent self ddos?

Could be, but they would be part of the minimal set to make a request work.