Group by / aggregate

Group an array of objects by one or more keys and aggregate a numeric field — count (default), sum, avg, min, or max. The SQL GROUP BY agents reach for when wrangling JSON. Deterministic (groups in first-seen order).

Input

Field	Type	Description
data *	any	array of objects (or JSON string)
by *	any	key name, or array of key names, to group by
field	string	numeric field to aggregate (omit for count only)
op	string	count (default) | sum | avg | min | max

Example output

{
  "groups": [
    {
      "key": {
        "city": "NYC"
      },
      "count": 2,
      "sum": 5
    },
    {
      "key": {
        "city": "LA"
      },
      "count": 1,
      "sum": 5
    }
  ],
  "count": 2
}

Try it — see the 402 challenge (free)

curl -i -X POST https://agent402.tools/api/group-by \
  -H "Content-Type: application/json" \
  -d '{"data":[{"city":"NYC","n":2},{"city":"LA","n":5},{"city":"NYC","n":3}],"by":"city","field":"n","op":"sum"}'

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/group-by", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "data": [
      {
        "city": "NYC",
        "n": 2
      },
      {
        "city": "LA",
        "n": 5
      },
      {
        "city": "NYC",
        "n": 3
      }
    ],
    "by": "city",
    "field": "n",
    "op": "sum"
  }),
});

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=group-by")).json();
let n = 0;
while (lz(createHash("sha256").update(c.challenge + ":" + n).digest()) < c.difficulty) n++;
await fetch("https://agent402.tools/api/group-by", { method: "POST", headers: { "X-Pow-Solution": c.token + ":" + n, "Content-Type": "application/json" }, body: JSON.stringify({"data":[{"city":"NYC","n":2},{"city":"LA","n":5},{"city":"NYC","n":3}],"by":"city","field":"n","op":"sum"}) });

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