61trust / 100

Et0 Hargreaves

by Farm & Garden Calc in Weather & location

x402 APIPassing, checked 1 h ago

Hargreaves reference evapotranspiration (mm/day) from max and min temperature, latitude and day of year.

GET
https://agri-calc.x402tookit.com/et0-hargreaves
Price
$0.02
per call in USDC
Uptime
64.3%
last 30 days
Response time
526 ms
579 ms slowest 5%
Last check
Passed
1 h ago, next in 5 h

Run a free test callHow to call it

Reliability

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How to call it

GET https://agri-calc.x402tookit.com/et0-hargreaves

Each call costs $0.02 in USDC on Polygon, paid with the request over x402.

Run a free test callOne unpaid request, the way an agent sends it. You see the payment challenge it gets back. Nothing is charged.

Example request

From the listing.

GET https://agri-calc.x402tookit.com/et0-hargreaves?dayOfYear=246&latitude=-20&tmaxC=21.5&tminC=12.3

Parameters

ParameterTypeRequiredDescription
dayOfYearnumberYesDay of year, 1 to 366
latitudenumberYesLatitude in degrees, -90 to 90 (south negative)
tmaxCnumberYesDaily maximum air temperature, Celsius
tminCnumberYesDaily minimum air temperature, Celsius

Example response

The provider's example. We can't check it without paying.

{
  "asOf": "2026-10-11T23:40:36.036Z",
  "degraded": false,
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "et0InchesPerDay": 0.12519,
  "et0MmPerDay": 3.1797,
  "extraterrestrialRadiationMJm2Day": 32.194,
  "extraterrestrialRadiationMmDay": 13.135,
  "meanTempC": 16.9,
  "notChecked": [
    "wind, humidity and cloud cover (Hargreaves uses temperature only, so it is rougher than Penman-Monteith)",
    "local calibration (accuracy is worse on coastal and humid sites)",
    "…1 more"
  ],
  "reasons": [
    "ET0 = 0.0023 x (Tmean + 17.8) x sqrt(Tmax - Tmin) x Ra, with Ra the extraterrestrial radiation in mm/day equivalent.",
    "A rough estimate from temperature alone; use it for planning, not scheduling to the millimetre."
  ],
  "source": "computed locally (Hargreaves and Samani 1985 with FAO-56 eq. 21 extraterrestrial radiation)",
  "summary": "Reference ET0 about 3.18 mm/day (0.125 in/day) at latitude -20, day 246.",
  "tempRangeC": 9.2,
  "verdict": "ET0_COMPUTED"
}

Call it from code

The curl command shows the payment challenge. The JavaScript and Python versions pay and call, and never pay more than $0.02.

curl: see the payment challenge
# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://agri-calc.x402tookit.com/et0-hargreaves?dayOfYear=246&latitude=-20&tmaxC=21.5&tminC=12.3'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://agri-calc.x402tookit.com/et0-hargreaves?dayOfYear=246&latitude=-20&tmaxC=21.5&tminC=12.3' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode
JavaScript: pay and call
// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.02 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.02" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.02 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fagri-calc.x402tookit.com%2Fet0-hargreaves
const res = await pay("https://agri-calc.x402tookit.com/et0-hargreaves?dayOfYear=246&latitude=-20&tmaxC=21.5&tminC=12.3");
console.log(res.status, await res.text());
Python: pay and call
# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.02 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.02"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://agri-calc.x402tookit.com/et0-hargreaves?dayOfYear=246&latitude=-20&tmaxC=21.5&tminC=12.3")
    print(res.status_code, res.text)

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