{"service":"llm-diff-explainer","version":"1.0.0","status":"ok","one_liner":"Semantic diff between two LLM responses with natural-language explanation — designed for AB tests and model migrations (Claude 4.5→4.7, GPT-5→5.4).","why_this_exists":"Text diffs show what changed. They never show *why it matters*. This API surfaces numeric-claim drift, named-entity churn, citation strip, tone-certainty shift, and structural changes — the actual reasons a model swap regresses in production.","endpoints":{"POST /diff":"Compare two responses (A, B). Returns headline, decision, similarity, metrics, findings.","POST /batch":"Compare up to 25 (free) / 200 (pro) pairs.","POST /api-key/generate":"Manually issue API key (requires x-admin-secret).","POST /webhook/gumroad":"Gumroad purchase webhook — auto-issues Pro/Team key.","GET /openapi.json":"OpenAPI 3.1 spec.","GET /healthz":"Liveness check.","GET /quota":"Current quota usage for your IP or API key."},"pricing":{"free":"500 comparisons/day per IP — no key required","pro":"$19/mo — unlimited + CSV export + webhook + priority support","team":"$49/mo per seat — model registry, bulk eval-set diffing"},"upgrade_url":"https://coindany4.gumroad.com/l/llm-diff-explainer-pro","example_curl":"curl -X POST https://api.lazy-mac.com/llm-diff-explainer/diff -H 'content-type: application/json' -d '{\"a\":\"The capital is Paris.\",\"b\":\"The capital is Lyon.\"}'"}