Calc Amortization

{
  "annual_rate_percent": 6.75,
  "extra_payment": 200,
  "first_12_payments": [
    {
      "balance": 299541.71,
      "interest": 1687.5,
      "month": 1,
      "payment": 2145.79,
      "principal": 458.29
    },
    {
      "balance": 299080.83,
      "interest": 1684.92,
      "month": 2,
      "payment": 2145.79,
      "principal": 460.87
    },
    {
      "balance": 298617.37,
      "interest": 1682.33,
      "month": 3,
      "payment": 2145.79,
      "principal": 463.46
    },
    {
      "balance": 298151.3,
      "interest": 1679.72,
      "month": 4,
      "payment": 2145.79,
      "principal": 466.07
    },
    {
      "balance": 297682.6,
      "interest": 1677.1,
      "month": 5,
      "payment": 2145.79,
      "principal": 468.69
    },
    {
      "balance": 297211.27,
      "interest": 1674.46,
      "month": 6,
      "payment": 2145.79,
      "principal": 471.33
    },
    {
      "balance": 296737.29,
      "interest": 1671.81,
      "month": 7,
      "payment": 2145.79,
      "principal": 473.98
    },
    {
      "balance": 296260.65,
      "interest": 1669.15,
      "month": 8,
      "payment": 2145.79,
      "principal": 476.65
    },
    {
      "balance": 295781.32,
      "interest": 1666.47,
      "month": 9,
      "payment": 2145.79,
      "principal": 479.33
    },
    {
      "balance": 295299.29,
      "interest": 1663.77,
      "month": 10,
      "payment": 2145.79,
      "principal": 482.02
    },
    {
      "balance": 294814.56,
      "interest": 1661.06,
      "month": 11,
      "payment": 2145.79,
      "principal": 484.74
    },
    {
      "balance": 294327.1,
      "interest": 1658.33,
      "month": 12,
      "payment": 2145.79,
      "principal": 487.46
    }
  ],
  "interest_saved_by_extra": 109927.52,
  "method": "fixed-rate level payment; monthly rate = annual rate / 12; excludes taxes, insurance and fees",
  "monthly_payment": 1945.79,
  "payoff_months": 276,
  "principal": 300000,
  "term_months": 360,
  "total_interest": 290558.43,
  "total_paid": 590558.43,
  "yearly": [
    {
      "balance": 294327.1,
      "interest_paid": 20076.63,
      "principal_paid": 5672.9,
      "year": 1
    },
    {
      "balance": 288259.2,
      "interest_paid": 19681.63,
      "principal_paid": 6067.9,
      "year": 2
    },
    {
      "balance": 281768.81,
      "interest_paid": 19259.14,
      "principal_paid": 6490.39,
      "year": 3
    },
    {
      "balance": 274826.5,
      "interest_paid": 18807.23,
      "principal_paid": 6942.3,
      "year": 4
    },
    {
      "balance": 267400.82,
      "interest_paid": 18323.85,
      "principal_paid": 7425.68,
      "year": 5
    },
    {
      "balance": 259458.1,
      "interest_paid": 17806.81,
      "principal_paid": 7942.72,
      "year": 6
    },
    {
      "balance": 250962.35,
      "interest_paid": 17253.78,
      "principal_paid": 8495.75,
      "year": 7
    },
    {
      "balance": 241875.05,
      "interest_paid": 16662.24,
      "principal_paid": 9087.29,
      "year": 8
    },
    {
      "balance": 232155.03,
      "interest_paid": 16029.51,
      "principal_paid": 9720.02,
      "year": 9
    },
    {
      "balance": 221758.22,
      "interest_paid": 15352.72,
      "principal_paid": 10396.81,
      "year": 10
    },
    {
      "balance": 210637.5,
      "interest_paid": 14628.81,
      "principal_paid": 11120.72,
      "year": 11
    },
    {
      "balance": 198742.47,
      "interest_paid": 13854.5,
      "principal_paid": 11895.03,
      "year": 12
    },
    {
      "balance": 186019.22,
      "interest_paid": 13026.27,
      "principal_paid": 12723.26,
      "year": 13
    },
    {
      "balance": 172410.07,
      "interest_paid": 12140.38,
      "principal_paid": 13609.15,
      "year": 14
    },
    {
      "balance": 157853.34,
      "interest_paid": 11192.8,
      "principal_paid": 14556.73,
      "year": 15
    },
    {
      "balance": 142283.05,
      "interest_paid": 10179.25,
      "principal_paid": 15570.28,
      "year": 16
    },
    {
      "balance": 125628.65,
      "interest_paid": 9095.12,
      "principal_paid": 16654.41,
      "year": 17
    },
    {
      "balance": 107814.62,
      "interest_paid": 7935.51,
      "principal_paid": 17814.02,
      "year": 18
    },
    {
      "balance": 88760.25,
      "interest_paid": 6695.16,
      "principal_paid": 19054.38,
      "year": 19
    },
    {
      "balance": 68379.16,
      "interest_paid": 5368.44,
      "principal_paid": 20381.09,
      "year": 20
    }
  ]
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://saylorinnovations.com/api/calc/amortization?extra_payment=200&principal=300000&rate=6.75&years=30'

# 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://saylorinnovations.com/api/calc/amortization?extra_payment=200&principal=300000&rate=6.75&years=30' \
  | 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 $0.01 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.01" });
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 $0.01 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fsaylorinnovations.com%2Fapi%2Fcalc%2Famortization
const res = await pay("https://saylorinnovations.com/api/calc/amortization?extra_payment=200&principal=300000&rate=6.75&years=30");
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 $0.01 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.01"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://saylorinnovations.com/api/calc/amortization?extra_payment=200&principal=300000&rate=6.75&years=30")
    print(res.status_code, res.text)