JSON validate & format

Validate, pretty-print, or minify JSON. Returns parse errors with position when invalid.

Input

Field	Type	Description
json *	string	JSON text to validate/format (max 100KB)
indent	number	Spaces of indentation; 0 = minify (default 2)

Example output

{
  "valid": true,
  "formatted": "{\n  \"a\": 1\n}"
}

Try it - see the 402 challenge (free)

curl -i -X POST https://agent402.tools/api/json-format \
  -H "Content-Type: application/json" \
  -d '{"json":"{\"a\":1}","indent":2}'

The response is HTTP 402 Payment Required with exact payment requirements. Any x402 v2 client pays automatically and retries:

Paid call (JavaScript agent)

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

const client = new x402Client();
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/json-format", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "json": "{\"a\":1}",
    "indent": 2
  }),
});

No wallet? Pay with compute

This is a pure-CPU tool, so an agent without a wallet can pay with proof-of-work instead of USDC: fetch a challenge, solve the sha256 puzzle (16 leading zero bits - a fraction of a second of CPU, no money, no AI tokens), and resend with the X-Pow-Solution header.

import { createHash } from "node:crypto";
const lz = (b) => { let t = 0; for (const x of b) { if (!x) { t += 8; continue; } t += Math.clz32(x) - 24; break; } return t; };
const c = await (await fetch("https://agent402.tools/api/pow/challenge?slug=json-format")).json();
let n = 0;
while (lz(createHash("sha256").update(c.challenge + ":" + n).digest()) < c.difficulty) n++;
await fetch("https://agent402.tools/api/json-format", { method: "POST", headers: { "X-Pow-Solution": c.token + ":" + n, "Content-Type": "application/json" }, body: JSON.stringify({"json":"{\"a\":1}","indent":2}) });

Part of these workflows

This tool is one step in 7 curated multi-tool workflows - agents can fetch the whole sequence as an MCP prompt or call https://agent402.tools/api/skill-packs/{slug}/prompt.

• Decode this blob - Hand the agent an opaque string - a JWT, a base64'd JSON payload, a gzip-encoded API response, a hex-encoded hash - and walk it through identifying what it is and unwrapping it layer by layer until it's human-readable.
• API investigation - Point at an unknown API endpoint and figure out how to use it: auth scheme, content type, version, rate limits, OpenAPI/Swagger spec discovery, and JSON response structure. The deterministic recon workflow before writing a single line of integration code.
• Webhook debug - A webhook hit your endpoint and you need to confirm it's authentic, valid, and safe to log. Pretty-print the payload, decode any JWT auth header, verify the HMAC signature against the raw body, schema-validate the parsed JSON, translate timestamps to human time, redact sensitive fields before they hit your log pipeline, and pull out URLs/emails/IPs for fast indexing. Seven pure-CPU tools - the canonical webhook-receiver debugging round-trip.
• XML to JSON - Convert XML to JSON and pretty-print it - the 'legacy API response to modern format' workflow in one call.
• JSON pipeline - Validate, pretty-print, and convert JSON to CSV in one pass - the complete JSON processing workflow.
• Data format converter - CSV to JSON to YAML pipeline - convert tabular data through the common interchange formats in one chain.
• Schema guard - Contract-test a JSON payload in one call: validate it against your schema, infer the schema the payload actually implies, diff the two to expose drift, and return a normalized pretty-print.

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