What's Splainer? Splainer is a relevance sandbox. It doesn't just parse the relevance explain, it tells you why. It decomposes the relevance explain into a summary of matches that matter most. Then from that top-level you drill down with more human-readable explanations of the explain output. If you're interested, read more in the blog post.
Here's the TLDR gif version of Splainer:
Splainer comes out of the search relevance practice of OpenSource Connections. Splainer is the baby brother of our relevance tuning product Quepid. Quepid is a test-driven relevance toolbench. It gives you all the functionality and insight of Splainer, but more holistically over all your candidate keyword searches. It keeps a history of all your relevance work and lets you snapshot and save results for later comparison.
Splainer is open source. Bugs and contributions welcome on github