The spec contains formal, numbered items which are requirements and also serve to make tests (these are spec tests, additional implementation tests are also allowed by the implementer). When I said "they are not formalized as much", I mean I am not as strict on the spec format as CodeSpeak is, where their spec can be parsed with a tool. For me it is up to the LLM to use the spec itself. I have additional text beyond the requirement items which also influences how the LLM implements the code. I did this because it is too tough, for me at least, to prompt the LLM just based on strict requirements. This is perhaps cheating according to what you might call SDD. I'm just trying to be practical. The idea in the end is that this spec implies the code and maintaining the spec is the same as maintaining the code. Strictly speaking this won't be true, but I am hoping it still works anyway.