Interval

{
  "asOf": "2026-10-11T14:26:13.737Z",
  "compound": false,
  "degraded": false,
  "descending": false,
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "from": "C4",
  "fullName": "major third",
  "interval": "M3",
  "inversion": "m6",
  "notChecked": [
    "tuning (an interval name says nothing about just or equal-tempered frequency ratios)",
    "intervals beyond triple augmented or diminished",
    "…1 more"
  ],
  "number": 3,
  "quality": "M",
  "reasons": [
    "Octaves given: compound intervals keep their full number.",
    "Quality comes from the letter names, so C to E is a major third but C to Fb is a diminished fourth."
  ],
  "semitones": 4,
  "simpleNumber": 3,
  "source": "computed locally",
  "summary": "C4 to E4: M3 (major third), 4 semitones.",
  "to": "E4",
  "verdict": "NAMED"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://music-theory.x402tookit.com/interval?from=C4&to=E4'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://music-theory.x402tookit.com/interval?from=C4&to=E4' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

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

// Pays at most $0.02 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.02" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.02 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fmusic-theory.x402tookit.com%2Finterval
const res = await pay("https://music-theory.x402tookit.com/interval?from=C4&to=E4");
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.02 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.02"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://music-theory.x402tookit.com/interval?from=C4&to=E4")
    print(res.status_code, res.text)