What it is
Identity / character document. Markdown file that carries the operator's stated values, philosophy, and operational constraints.
MD-aware Claude Code prompts). The character file.
Where it sits
SOUL.MD is catalogued under Brand & Public in the instrument registry. Instruments in this group share a concern and are frequently composed rather than used alone; the related entries below are the nearest ones.
This is a registry entry: a real instrument, documented here, without a public endpoint a stranger can open. Pages carrying source excerpts and measured results are marked as such in the catalog. If you want detail on this one specifically, ask about it directly.