curl --request POST \
  --url https://api.rivermarkets.com/v1/fair-values \
  --header 'Content-Type: application/json' \
  --header 'X-River-Key-Id: <api-key>' \
  --header 'X-River-Signature: <api-key>' \
  --header 'X-River-Timestamp: <api-key>' \
  --data '
{
  "subaccount_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "fair_values": [
    {
      "river_id": 123,
      "fair_value": 0.5
    }
  ]
}
'

import requests

url = "https://api.rivermarkets.com/v1/fair-values"

payload = {
    "subaccount_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "fair_values": [
        {
            "river_id": 123,
            "fair_value": 0.5
        }
    ]
}
headers = {
    "X-River-Key-Id": "<api-key>",
    "X-River-Timestamp": "<api-key>",
    "X-River-Signature": "<api-key>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {
    'X-River-Key-Id': '<api-key>',
    'X-River-Timestamp': '<api-key>',
    'X-River-Signature': '<api-key>',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    subaccount_id: '3c90c3cc-0d44-4b50-8888-8dd25736052a',
    fair_values: [{river_id: 123, fair_value: 0.5}]
  })
};

fetch('https://api.rivermarkets.com/v1/fair-values', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.rivermarkets.com/v1/fair-values",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'subaccount_id' => '3c90c3cc-0d44-4b50-8888-8dd25736052a',
    'fair_values' => [
        [
                'river_id' => 123,
                'fair_value' => 0.5
        ]
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json",
    "X-River-Key-Id: <api-key>",
    "X-River-Signature: <api-key>",
    "X-River-Timestamp: <api-key>"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.rivermarkets.com/v1/fair-values"

	payload := strings.NewReader("{\n  \"subaccount_id\": \"3c90c3cc-0d44-4b50-8888-8dd25736052a\",\n  \"fair_values\": [\n    {\n      \"river_id\": 123,\n      \"fair_value\": 0.5\n    }\n  ]\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("X-River-Key-Id", "<api-key>")
	req.Header.Add("X-River-Timestamp", "<api-key>")
	req.Header.Add("X-River-Signature", "<api-key>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://api.rivermarkets.com/v1/fair-values")
  .header("X-River-Key-Id", "<api-key>")
  .header("X-River-Timestamp", "<api-key>")
  .header("X-River-Signature", "<api-key>")
  .header("Content-Type", "application/json")
  .body("{\n  \"subaccount_id\": \"3c90c3cc-0d44-4b50-8888-8dd25736052a\",\n  \"fair_values\": [\n    {\n      \"river_id\": 123,\n      \"fair_value\": 0.5\n    }\n  ]\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.rivermarkets.com/v1/fair-values")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["X-River-Key-Id"] = '<api-key>'
request["X-River-Timestamp"] = '<api-key>'
request["X-River-Signature"] = '<api-key>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"subaccount_id\": \"3c90c3cc-0d44-4b50-8888-8dd25736052a\",\n  \"fair_values\": [\n    {\n      \"river_id\": 123,\n      \"fair_value\": 0.5\n    }\n  ]\n}"

response = http.request(request)
puts response.read_body

{
  "fair_values": [
    {
      "subaccount_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "river_id": 123,
      "fair_value": 123,
      "updated_at": "<string>"
    }
  ]
}

{
  "detail": [
    {
      "loc": [
        "<string>"
      ],
      "msg": "<string>",
      "type": "<string>",
      "input": "<unknown>",
      "ctx": {}
    }
  ]
}