Reciprocal rank fusion (RRF)
A way to merge ranked lists by adding 1/(k + rank) for each list an item appears in.
What it means
Reciprocal rank fusion merges several ranked lists without needing comparable scores. Each item scores 1 / (k + r) for its position r in every list it appears in, and the scores are summed. An item near the top of several lists beats one at the very top of a single list.
How Onekey handles it
Add fuse=rrf to /v1/search/multi and the answer gains data.fused, using k = 60. It is arithmetic over the order each platform returned, with no text analysis and no judgement of relevance. Rank 1 scores 0.016393, and first on one platform plus fourth on another scores 0.032018.