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YouTube Transcript Lexical Search — Melchior Labs
x402
YouTube Transcript Lexical Search — Melchior Labs is a paid API for AI agents from transcript.melchiorlabs.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-22).
Searches a YouTube video's transcript for passages matching a query, returning ranked text snippets with timestamp citations.
Price / call$0.005
Success—
StatusUnknown
How this service works
Pay per request for structured YouTube transcripts, lexical passage search, chunks, and timestamp citations over x402.
Output
Returns a ranked list of transcript passage matches, each with the matched text, a score, the specific terms matched, start and end timestamps in seconds, and a direct YouTube URL with a timestamp parameter (e.g. &t=42s). Also includes video metadata (ID, title, URL), usage stats (cache hit/miss, segment counts), and a request ID for tracing.
Example use cases
Fact-check a speaker's claim in a lecture
“In this university lecture on YouTube (https://www.youtube.com/watch?v=abc123XYZ), find every passage where the professor mentions 'placebo effect' — give me the timestamps so I can jump straight to those moments, top 5 results please.”
Pull a quote with citation from a podcast
“I need the exact words and a timestamp link for when the guest in this podcast (https://www.youtube.com/watch?v=pod456ABC) talks about 'supply chain disruption' — search the English transcript and return the top 2 matches with surrounding context.”
Locate a coding tutorial step by timestamp
“In this Python tutorial video (https://youtu.be/tut789DEF), find where the instructor explains 'list comprehension' and give me the timestamp so I can link directly to that part of the video.”
Technical details
Endpoint
POSThttps://transcript.melchiorlabs.com/v1/youtube/search?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need to find specific passages, quotes, or topic mentions within a single YouTube video by keyword or phrase, and you want timestamped citations back. It is purpose-built for lexical transcript search with citation output, making it ideal for research, fact-checking, podcast navigation, or linking directly to a moment in a video. Prefer it over generic transcript-fetch endpoints when you need ranked relevance and timestamp links rather than a full raw transcript dump.
Side effects
- Video is private or unavailable — transcript cannot be fetched
- No captions available in the requested language — returns empty matches or error
- Query returns zero matches if none of the terms appear in the transcript
- Invalid YouTube URL format — rejected by pattern validation
- maxResults or contextSegments out of allowed range — schema validation error
- Rate limiting or payment failure over x402 protocol
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| url | string | Public youtube.com or youtu.be video URL |
| query | string | Phrase or terms to match lexically in the transcript |
| language | string | Caption language code, such as en or es |
| maxResults | integer | |
| preferManual | boolean | |
| contextSegments | integer |
Output
Schema · Response
{
"type": "json",
"example": {
"query": "never gonna give you up",
"usage": {
"cache": "hit",
"matchedSegments": 2,
"returnedMatches": 1,
"candidateSegments": 60
},
"video": {
"id": "dQw4w9WgXcQ",
"url": "https://www.youtube.com/watch?v=dQw4w9WgXcQ",
"title": "Video title"
},
"matches": [
{
"rank": 1,
"text": "Never gonna give you up...",
"score": 17,
"citation": {
"url": "https://www.youtube.com/watch?v=dQw4w9WgXcQ&t=42s",
"label": "0:42–0:49"
},
"endSeconds": 49,
"matchedTerms": [
"give",
"never"
],
"startSeconds": 42
}
],
"requestId": "0b0ef10e-ff50-4a45-9c4e-b7344aa93f63"
}
}Tags
x402
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