Suggestions:

Put the parameters into the url so searches can be bookmarked, like zip codes, terms, filters, and other aspects can be shared easily.

Description search both include (like i7, 16GB) which is good for electronics and exclude for example exclude "repair" or "needs repair" which is helpful for many things.

Category specific filters, vehicle millage range, year

Keywords like pickup, delivery, payment methods, etc.

You are probably already thinking along these lines for some of them, just an encouragement to implement. Yes categories can be fuzzy(commas, which word or plurals used, etc), so feel free to put the [beta] or [experimental] tag until a recipe that gets most of the stuff works.

Thanks for building this, I bookmarked it and already shared it with a few friends.