Media Contrast Check

{
  "result": {
    "answer": "2.54:1 — 0/5 WCAG thresholds pass",
    "answerLabel": "Contrast ratio",
    "details": [
      {
        "label": "Foreground luminance",
        "value": "1.0000"
      },
      {
        "label": "Background luminance",
        "value": "0.3639"
      },
      {
        "label": "Formula",
        "value": "(L1 + 0.05) / (L2 + 0.05)"
      }
    ],
    "steps": [
      "WCAG relative luminance for each color",
      "Ratio = (1.0000 + 0.05) / (0.3639 + 0.05) = 2.54"
    ],
    "table": {
      "columns": [
        "Threshold",
        "Pass"
      ],
      "rows": [
        [
          "AA normal text (≥4.5)",
          "✗"
        ],
        [
          "AA large text (≥3.0)",
          "✗"
        ],
        [
          "AAA normal text (≥7.0)",
          "✗"
        ],
        [
          "AAA large text (≥4.5)",
          "✗"
        ],
        [
          "UI components (≥3.0)",
          "✗"
        ]
      ]
    },
    "value": 2.54
  },
  "tool": "contrast-check"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://agentstoolshub.com/api/v1/media/contrast-check?background=%2310b981&foreground=%23ffffff'

# 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://agentstoolshub.com/api/v1/media/contrast-check?background=%2310b981&foreground=%23ffffff' \
  | 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 $0.002 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.002" });
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 $0.002 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fagentstoolshub.com%2Fapi%2Fv1%2Fmedia%2Fcontrast-check
const res = await pay("https://agentstoolshub.com/api/v1/media/contrast-check?background=%2310b981&foreground=%23ffffff");
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 $0.002 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.002"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://agentstoolshub.com/api/v1/media/contrast-check?background=%2310b981&foreground=%23ffffff")
    print(res.status_code, res.text)