JSON validate & format

Validate, pretty-print (any indentation, 0-8 spaces), or minify JSON, optionally with object keys sorted. canonical: true returns the RFC 8785 (JCS) canonical form - keys sorted, no whitespace, ECMAScript number and string serialization - plus its SHA-256, for hashing and signing. Send POST /api/json-format with the required field json and pay $0.001 per call over x402 or MPP, or call it free by solving a proof-of-work challenge. It returns a JSON object with valid and formatted.

Numbers are read as IEEE-754 doubles and a duplicate key keeps its last value. Returns parse errors with position when invalid.

Category: Data conversion · Tags: json format validate canonical pretty-print minify sort-keys · Also found as: pretty-print prettify minify indent

TRY IN PLAYGROUND →

Parameters

Example request

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

Without payment this returns HTTP 402 Payment Required with the exact price for json-format; any x402 v2 or MPP client pays it and retries.

Example response

{
  "valid": true,
  "formatted": "{\n  \"a\": 1,\n  \"b\": 2\n}"
}

From an MCP client

catalog.call {
  "slug": "json-format",
  "params": {
    "json": "{\"b\":2,\"a\":1}",
    "indent": 2,
    "sortKeys": true
  }
}

On the hosted connector at https://agent402.tools/mcp, catalog.call runs json-format free (rate-limited, no wallet). Local install: npx -y agent402-mcp.

Errors and behavior

• json is required. An input the tool rejects returns an HTTP 4xx whose body carries error, tool, expected, required and example, so the caller can correct it.
• A paid call that ends in any status of 400 or above is not charged over x402, MPP or a prepaid credits key: settlement is cancelled when the tool fails. The exception is a Tempo push credential, a transfer the buyer sent before the call: it settles before the tool runs, so if the tool then fails the payment is recorded as a refund owed to the paying wallet.
• Free tier: no outbound network call leaves the server for this tool, so proof-of-work (16 leading zero bits of sha256) pays for it.
• A GET or HEAD to /api/json-format returns the same 402 quote, so the price can be read without a body.
• An Idempotency-Key header makes a retried paid call replay the first 200 instead of charging again (an answer larger than 1 MB is not replayed).

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();
client.setSpendControls?.(false); // keep your own spending ceiling in code
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": "{\"b\":2,\"a\":1}",
    "indent": 2,
    "sortKeys": true
  }),
});

No wallet? Pay with compute

Fetch a challenge, solve the sha256 puzzle (16 leading zero bits, a fraction of a second of CPU), 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":"{\"b\":2,\"a\":1}","indent":2,"sortKeys":true}) });

Part of these workflows

JSON validate & format is one step in these 4 skill packs, each sold as a single call:

• 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.
• 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.
• JSON pipeline - Validate, pretty-print, and convert JSON to CSV in one pass - the complete JSON processing workflow.

Related tools