Hit this exact wall six months back building Claude Code stuff for KiCad review[1]. First pass let Claude read .kicad_sch directly via grep/read. It happily invented pin numbers that didn't exist. Rewrote it with Python analyzers that spit out JSON, now Claude just reads the JSON, problem mostly went away.
Curious how spicelib-mcp handles models that aren't in the bundled library. Do you pass the .lib path as a tool arg, or does the server own a registry?