Precious-Metal Ratios API

The ratios between gold, silver, platinum and palladium, where they sit in their own multi-year history, and which metal is cheap relative to which — computed live from Yahoo Finance futures, no key, nothing stored. A precious-metal price tells you what an ounce costs; the ratio between two metals tells you which is expensive relative to the other — and these ratios are famously mean-reverting, which is why the gold/silver "mint ratio" is one of the oldest trades there is: when it stretches to an extreme, traders rotate from the dear metal into the cheap one and ride it back. A single current ratio is only half the story; what matters is where that ratio sits in its multi-year range. This API computes the gold/silver, gold/platinum, platinum/palladium, gold/palladium and silver/platinum ratios, and for each returns its current value, its percentile within a multi-year window (the context that turns a number into a signal), the window min/max/average, and a plain-language rotation read — at a high percentile the numerator metal is historically expensive (favour the denominator), at a low percentile the reverse. The ratios endpoint returns the whole complex; the ratio endpoint returns one pair with its component prices; the history endpoint returns the ratio time series. This is the precious-metal-ratio / mean-reversion cut — distinct from the inter-commodity crack/crush spread API (which gives the current gold/silver ratio but no history, percentile or signal), the intermarket-ratio board and the metals spot-price feed. It is the ratio with its history attached.