Subtitle convert (SRT/VTT)

Convert subtitles between SRT, WebVTT, plain text, and JSON cues. Send SRT or VTT text (auto-detected) — or a JSON cues array [{start,end,text}] with times in ms — and the target format. Deterministic, pure CPU.

Input

Field	Type	Description
input	string	SRT or WebVTT text (format auto-detected)
cues	array	alternative: cue objects [{start,end,text}] with start/end in milliseconds
to *	string	target format: srt | vtt | text | json

Example output

{
  "detected": "srt",
  "to": "vtt",
  "count": 2,
  "result": "WEBVTT\n\n00:00:01.000 --> 00:00:03.000\nHello world\n\n00:00:03.500 --> 00:00:05.000\nSecond line\n"
}

Try it — see the 402 challenge (free)

curl -i -X POST https://agent402.tools/api/srt-convert \
  -H "Content-Type: application/json" \
  -d '{"input":"1\n00:00:01,000 --> 00:00:03,000\nHello world\n\n2\n00:00:03,500 --> 00:00:05,000\nSecond line\n","to":"vtt"}'

The response is HTTP 402 Payment Required with exact payment requirements. Any x402 v2 client pays automatically and retries:

Paid call (JavaScript agent)

import { wrapFetchWithPayment } from "@x402/fetch";
import { x402Client } from "@x402/core/client";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const client = new x402Client();
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/srt-convert", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "input": "1\n00:00:01,000 --> 00:00:03,000\nHello world\n\n2\n00:00:03,500 --> 00:00:05,000\nSecond line\n",
    "to": "vtt"
  }),
});

No wallet? Pay with compute

This is a pure-CPU tool, so an agent without a wallet can pay with proof-of-work instead of USDC: fetch a challenge, solve the sha256 puzzle (16 leading zero bits — a fraction of a second of CPU, no money, no AI tokens), and resend with the X-Pow-Solution header.

import { createHash } from "node:crypto";
const lz = (b) => { let t = 0; for (const x of b) { if (!x) { t += 8; continue; } t += Math.clz32(x) - 24; break; } return t; };
const c = await (await fetch("https://agent402.tools/api/pow/challenge?slug=srt-convert")).json();
let n = 0;
while (lz(createHash("sha256").update(c.challenge + ":" + n).digest()) < c.difficulty) n++;
await fetch("https://agent402.tools/api/srt-convert", { method: "POST", headers: { "X-Pow-Solution": c.token + ":" + n, "Content-Type": "application/json" }, body: JSON.stringify({"input":"1\n00:00:01,000 --> 00:00:03,000\nHello world\n\n2\n00:00:03,500 --> 00:00:05,000\nSecond line\n","to":"vtt"}) });

Part of these workflows

This tool is one step in a curated multi-tool workflow — agents can fetch the whole sequence as an MCP prompt or call https://agent402.tools/api/skill-packs/{slug}/prompt.

• Subtitle pipeline — Audio URL → finished subtitles in one call: transcribe the audio, emit the transcript as SRT/WebVTT/JSON cues, and report the text statistics — length, reading time, word count.

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