Forecast (naive baselines)

Three textbook baseline forecasts: mean (forecast = average of history), naive (forecast = last value), drift (linear extrapolation from first to last point). Use as a sanity floor — any sophisticated method (SES, Holt, Holt-Winters) should beat the best of these on a backtest, otherwise the extra complexity isn't earning its keep. Returns point forecasts + 95% prediction intervals per Hyndman §3.1.

Input

Field	Type	Description
values *	array	Numeric series in chronological order (max 10000)
horizon *	number	Number of future periods to forecast (1 to 1000)
method	string	"mean", "naive", or "drift" (default "drift")

Example output

{
  "method": "drift",
  "n": 10,
  "horizon": 3,
  "forecast": [
    {
      "step": 1,
      "point": 23.3333,
      "lower95": 21.8037,
      "upper95": 24.863
    },
    {
      "step": 2,
      "point": 24.6667,
      "lower95": 22.3979,
      "upper95": 26.9355
    },
    {
      "step": 3,
      "point": 26,
      "lower95": 23.0977,
      "upper95": 28.9023
    }
  ]
}

Try it — see the 402 challenge (free)

curl -i -X POST https://agent402.tools/api/forecast-naive \
  -H "Content-Type: application/json" \
  -d '{"values":[10,12,13,12,15,16,18,19,21,22],"horizon":3,"method":"drift"}'

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/forecast-naive", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "values": [
      10,
      12,
      13,
      12,
      15,
      16,
      18,
      19,
      21,
      22
    ],
    "horizon": 3,
    "method": "drift"
  }),
});

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=forecast-naive")).json();
let n = 0;
while (lz(createHash("sha256").update(c.challenge + ":" + n).digest()) < c.difficulty) n++;
await fetch("https://agent402.tools/api/forecast-naive", { method: "POST", headers: { "X-Pow-Solution": c.token + ":" + n, "Content-Type": "application/json" }, body: JSON.stringify({"values":[10,12,13,12,15,16,18,19,21,22],"horizon":3,"method":"drift"}) });

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