Text-to-speech (HD)

Convert text to speech with the eleven-v4 model, priced per request from the length of the text. Send POST /api/tts-hd with the required field text and pay quoted per request from $0.01 over x402 or MPP (there is no free tier). It returns a JSON object with model, provider, voice, format, audio and 1 more.

It is the most expressive speech tier, and the quote is $0.010 plus $0.115 per 1,000 characters of text, rounded up to the next $0.001 (2,000 characters: $0.240). Inline audio tags such as [whispering] are read as delivery cues. Returns base64-encoded audio. Same interface, voices, formats and backups as /api/tts. No API key needed; pay per call via x402 or MPP. Text capped at 2000 chars. Model-backed.

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Parameters

Example request

curl -i -X POST https://agent402.tools/api/tts-hd \
  -H "Content-Type: application/json" \
  -d '{"text":"Hello from Agent402!","voice":"alloy","format":"mp3"}'

Without payment this returns HTTP 402 Payment Required with the exact price for tts-hd; any x402 v2 or MPP client pays it and retries.

Example response

{
  "model": "elevenlabs/eleven-v4",
  "provider": "openrouter",
  "voice": "river",
  "format": "mp3",
  "audio": "<base64-encoded audio>",
  "chars": 20
}

From an MCP client

catalog.call {
  "slug": "tts-hd",
  "params": {
    "text": "Hello from Agent402!",
    "voice": "alloy",
    "format": "mp3"
  }
}

The hosted connector at https://agent402.tools/mcp needs a payment for tts-hd; the stdio package pays it from a wallet or from an AGENT402_CREDITS_KEY issued earlier. Local install: npx -y [email protected].

Errors and behavior

• text is required. An input the tool rejects returns an HTTP 4xx whose body carries error, tool, expected, required and example, so the caller can correct it.
• A paid call that ends in any status of 400 or above is not charged over x402, MPP or a prepaid credits key: settlement runs after the tool and only on a successful response. The exception is a Tempo push credential, a transfer the buyer sent before the call: it settles before the tool runs, so if the tool then fails the payment is recorded as a refund owed to the paying wallet.
• Wallet-only: this tool runs a model, so it has no proof-of-work tier. A prepaid card-credits key issued earlier (Authorization: Bearer a402_...) also pays it.
• Model-backed: the answer is generated by a model, so the same input can produce a different result.
• Sales tax: the price includes North Carolina sales tax for a buyer billed to a North Carolina address by card (a prepaid credits key or a card payment per call).
• Priced per request: the 402 quotes this body, between $0.01 and $0.24. The quote is $0.010 plus $0.115 per 1,000 characters of text, rounded up to the next $0.001 (2,000 characters: $0.240).
• A GET or HEAD to /api/tts-hd returns the same 402 quote, so the price can be read without a body.
• An Idempotency-Key header makes a retried paid call replay the first 200 instead of charging again (an answer larger than 1 MB is not replayed).

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();
client.setSpendControls?.({ maxAmountPerPayment: "$0.24" }); // refuse any quote above this tool's price
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/tts-hd", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "text": "Hello from Agent402!",
    "voice": "alloy",
    "format": "mp3"
  }),
});

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