NFT Rarity Calculator

Samples tokenURI metadata directly and builds the trait frequency table locally, so the numbers cannot be shaped by whoever pays for marketplace placement. Handles IPFS URIs and inline base64 metadata. Scores individual tokens by the standard sum-of-inverse-frequency method. Fetches sequentially rather than in parallel, because a few hundred simultaneous gateway requests get rate-limited and a half-sampled collection gives wrong rarity. Rarity is computed from the tokens actually sampled, so percentages are within that sample rather than the whole collection — a larger sample gives a truer picture and takes longer. Collections whose metadata sits behind a gateway that rate-limits will return partial results, which are marked as such.