Sizeguide

• Recommend Size — Recommend a size from body measurements against a provenance-labeled size chart. Deterministic: identical input always returns the identical answer, with a confidence score, its four published factors, and a per-zone explanation. The engine may DECLINE: out-of-range or under-specified input returns kind:"guidance" with a message (and missingInputs when applicable) instead of a size — never a guess. Treat a guidance result as the answer, not an error; relay it to the user.
• Convert Size — Convert a size label between sizing systems through a caller-supplied conversion table (table-driven; no formulas). Returns the converted value with method "exact" or "interpolated" and the table's provenance riding along. DECLINES honestly: a value outside the table's bounds returns ok:false with a reason instead of an extrapolated guess.
• Get Size Chart — Fetch a published size chart by slug: versioned, content-hashed rows with explicit row semantics (body vs garment measurements) and a provenance tier (official_brand | manufacturer_published | sizeguide_reference — no fourth state). An unknown slug returns a 404 error, never an invented chart.
• Explain Fit — Explain how a set of body measurements fits a size chart. Runs the same deterministic recommendation as recommend_size and relays ONLY the explanation the engine itself produced: the per-zone verdicts, the summary rendered verbatim on every SizeGuide surface, any disclosed adjustments, and the confidence factors. Nothing is generated here that the engine did not return. When the engine DECLINES (out-of-range or under-specified input), the result is that guidance, verbatim — relay it as the expla

Schemas and invoke metadata: Directory API