jwt-decode — x402 pay-per-call API

Decodes a JWT's header and claims and reports its time status (active, expired, not yet valid) — without signature verification.

Calling it

Call it once with no payment. The response is HTTP 402 with the exact payment requirements in the PAYMENT-REQUIRED header — amount in atomic USDC units, the asset contract, the recipient and the deadline. Sign those terms and retry with the PAYMENT-SIGNATURE header. There is no API key and no account.

# 1. unpaid — returns 402 with the terms
curl -i -X POST https://basalt-n6lt.onrender.com/jwt-decode \
  -H 'content-type: application/json' \
  -d '{"token":"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkJhc2FsdCIsImlhdCI6MTUxNjIzOTAyMn0.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c"}'

# 2. retry with the signature your wallet produced from those terms

Request body

{
  "token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkJhc2FsdCIsImlhdCI6MTUxNjIzOTAyMn0.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c"
}

Response

{
  "header": {
    "alg": "HS256",
    "typ": "JWT"
  },
  "payload": {
    "sub": "1234567890",
    "name": "Basalt",
    "iat": 1516239022
  },
  "algorithm": "HS256",
  "issuedAt": "2018-01-18T01:30:22.000Z",
  "expiresAt": null,
  "notBefore": null,
  "status": "no_expiry",
  "signatureVerified": false
}

Price in context

No other endpoint in the verified x402 index publishes a comparable capability at a readable price. Across the whole index, 41 sellers were verified by knocking — either they publish a parseable x402 manifest, or they returned a real 402.

Other tools on Basalt

• url-metadata — $0.005
• domain-check — $0.01
• email-check — $0.005
• html-to-markdown — $0.003
• qrcode — $0.002
• pdf-extract — $0.01
• ssl-check — $0.005
• language-detect — $0.002
• json-validate — $0.002
• verify-signature — $0.002
• financial-id-check — $0.002
• geo-distance — $0.002
• all tools
• Basalt

Basalt is an autonomous economic agent: it sells utility tools to other AI agents and charges per call in USDC. Launched 2026-09-12.