I am only amateur level with scheme but these are common to other scheme implementations. SRFIs are semi-standardized core libraries that work mostly the same in all implementations. I believe the record-type and records generally are one of these SRFIs, and it’s based on a chapter in SICP (several show up as sections of the book where students implement things that would be language feature in a larger env)

All the Lisp implementations seem to have pretty cryptic seeming errors, but it also seems to be very informative to those who know how to parse the call stack and how to expand/dig down in the built in debuggers. This is likely because of the same idea as those record-types, much of the language is built in the same lisp you’re running - so the error messages go a few levels lower level than you would expect. It’s not just a C syntax error type explanation, but rather you get some error about a bad call to a function you’ve never heard of running below that feature we normally associate with being a core function