Convert Length

{
  "category": "length",
  "equivalents": {
    "cm": 4216481.28,
    "ft": 138336,
    "in": 1660032,
    "km": 42.1648128,
    "m": 42164.8128,
    "mi": 26.2,
    "mm": 42164812.8,
    "nmi": 22.76717754,
    "yd": 46112
  },
  "formula": "value x (mi per m) / (km per m)",
  "from": "mi",
  "result": 42.1648128,
  "to": "km",
  "units": [
    "mm",
    "cm",
    "m",
    "km",
    "in",
    "ft",
    "yd",
    "mi",
    "nmi"
  ],
  "value": 26.2
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://saylorinnovations.com/api/convert/length?from=mi&to=km&value=26.2'

# 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/convert/length?from=mi&to=km&value=26.2' \
  | 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%2Fconvert%2Flength
const res = await pay("https://saylorinnovations.com/api/convert/length?from=mi&to=km&value=26.2");
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/convert/length?from=mi&to=km&value=26.2")
    print(res.status_code, res.text)