JSON Validate, Repair, Convert,

Every AI agent and developer runs into broken or confusing JSON constantly. This tool handles all the most common JSON headaches in one place: check if JSON is valid (with exact error location), fix near-JSON that has typos or formatting mistakes, pretty-print or minify, pull out specific values using a path expression, compare two JSON documents and see exactly what changed, convert to and from YAML or CSV, produce a byte-stable canonical form for hashing or signing, validate against a schema, and get size and structure statistics. Same input always gives the same output — fully predictable, no side effects.

Call it in 30 seconds

// npm i x402-fetch viem
import { wrapFetchWithPayment } from "x402-fetch";
import { createWalletClient, http } from "viem";
import { privateKeyToAccount } from "viem/accounts";
import { base } from "viem/chains";

const account = privateKeyToAccount(process.env.PRIVATE_KEY); // funds USDC on Base
const wallet = createWalletClient({ account, chain: base, transport: http() });
const fetchWithPay = wrapFetchWithPayment(fetch, wallet);

// Pays the $0.01 USDC automatically on the 402, then returns the real response:
const res = await fetchWithPay("https://json-suite.underscoredone.com/json", { method: "POST" });
console.log(await res.json());

# pip install x402 eth-account httpx
import os, asyncio
from eth_account import Account
from x402.clients.httpx import x402HttpxClient

account = Account.from_key(os.environ["PRIVATE_KEY"])  # funds USDC on Base

async def main():
    async with x402HttpxClient(account=account) as client:
        # x402 handles the 402 -> pay ($0.01 USDC) -> retry automatically
        r = await client.get("https://json-suite.underscoredone.com/json")
        print((await r.aread()).decode())

asyncio.run(main())

# 1) An unpaid request returns HTTP 402 with the exact payment terms:
curl -i -X POST "https://json-suite.underscoredone.com/json" \
  -H 'content-type: application/json' \
  -d '{"data": {"order": {"id": "A-1029", "items": [{"qty": 2, "sku": "BIL-CUE-07"}, {"qty": 5, "sku": "BIL-CHALK-01"}]}}, "op": "query", "options": {"jsonpath": "$.order.items[*].sku"}}'

# 2) Paying + retrying requires an x402 client that can sign the USDC
#    authorization (curl alone cannot). See the JS / Python tabs below.

New to x402? Read the 5-minute quickstart →