# YouTube Transcript Context Chunker — Melchior Labs

> YouTube Transcript Context Chunker — Melchior Labs is a paid API for AI agents from transcript.melchiorlabs.com, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-24).

Accepts a raw YouTube transcript (text, VTT, or SRT) and returns structured, timestamped chunks with citation labels suitable for RAG, passage search, or agent context injection.

## Facts

- Endpoint: POST https://transcript.melchiorlabs.com/v1/transcripts/context?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-24
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/youtube-transcript-context-chunker-melchior-labs-042c3513
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_8vxG-ozBmL5yRHHvCiNt_

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability youtube-transcript-context-chunker-melchior-labs-042c3513 -d '<json body>'
```

Example prompt: Take this YouTube transcript in VTT format and break it into chunks of up to 2400 characters each, with timestamp citations like '0:00–0:30' so I can use them as cited sources in my RAG pipeline.

## When to prefer this

Choose this endpoint when you have a raw YouTube transcript (in plain text, VTT, or SRT format) and need it converted into structured, timestamped, citation-ready chunks for downstream RAG, passage retrieval, or LLM context injection. It is especially useful when you need precise start/end second metadata and human-readable citation labels per chunk. Prefer it over generic text splitters when working specifically with video transcripts that require temporal grounding.

## Known failure modes

- Missing or empty 'text' or 'segments' field returns a validation error
- Transcript exceeding 1,000,000 characters may be rejected or truncated
- Invalid format enum value (not 'text', 'vtt', or 'srt') causes a schema validation error
- Malformed VTT or SRT input may result in empty or incorrect segment parsing
- maxChunkCharacters outside 400–8000 range triggers a validation error
- Network or payment authorization failure (x402) returns a 402 response before processing

## How this service works

Pay per request for structured YouTube transcripts, lexical passage search, chunks, and timestamp citations over x402.

## Output

Returns an array of transcript chunks, each with its text content, zero-based index, start/end time in seconds, and a human-readable citation label (e.g. '0:00–0:03'). Also returns aggregated usage stats including total character count, chunk count, and estimated token count, plus a unique requestId and a top-level transcript summary with total segment count and full text.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "text": {
   "type": "string",
   "maxLength": 1000000,
   "description": "Plain text, WebVTT, or SRT transcript"
  },
  "format": {
   "enum": [
    "text",
    "vtt",
    "srt"
   ],
   "type": "string",
   "default": "text"
  },
  "segments": {
   "type": "array",
   "items": {
    "type": "object",
    "required": [
     "startSeconds",
     "endSeconds",
     "text"
    ],
    "properties": {
     "text": {
      "type": "string",
      "description": "Transcript text spoken during this segment."
     },
     "endSeconds": {
      "type": "number",
      "description": "Segment end time in seconds from the beginning of the source."
     },
     "startSeconds": {
      "type": "number",
      "description": "Segment start time in seconds from the beginning of the source."
     }
    }
   },
   "maxItems": 20000
  },
  "sourceUrl": {
   "type": "string",
   "pattern": "^https?://"
  },
  "includeText": {
   "type": "boolean",
   "default": true
  },
  "includeSegments": {
   "type": "boolean",
   "default": true
  },
  "maxChunkCharacters": {
   "type": "integer",
   "default": 2400,
   "maximum": 8000,
   "minimum": 400
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "usage": {
   "characters": 14,
   "chunkCount": 1,
   "estimatedTokens": 4
  },
  "chunks": [
   {
    "text": "Hello, agents.",
    "index": 0,
    "citation": {
     "label": "0:00–0:03"
    },
    "endSeconds": 3,
    "startSeconds": 0
   }
  ],
  "requestId": "89416332-bc4e-43da-b0e2-32af08677d9e",
  "transcript": {
   "text": "Hello, agents.",
   "segmentCount": 1
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/youtube-transcript-context-chunker-melchior-labs-042c3513/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from transcript.melchiorlabs.com](https://www.zero.xyz/host/transcript.melchiorlabs.com/llms.txt)