curl --request POST \
  --url https://api-sandbox.circle.com/v1/payouts/{id}/rfi/{rfiId}/submit \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "fields": {
    "purposeOfFunds": "payroll",
    "sourceOfFunds": "business_revenue"
  }
}
'

import requests

url = "https://api-sandbox.circle.com/v1/payouts/{id}/rfi/{rfiId}/submit"

payload = { "fields": {
        "purposeOfFunds": "payroll",
        "sourceOfFunds": "business_revenue"
    } }
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({fields: {purposeOfFunds: 'payroll', sourceOfFunds: 'business_revenue'}})
};

fetch('https://api-sandbox.circle.com/v1/payouts/{id}/rfi/{rfiId}/submit', 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-sandbox.circle.com/v1/payouts/{id}/rfi/{rfiId}/submit",
  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([
    'fields' => [
        'purposeOfFunds' => 'payroll',
        'sourceOfFunds' => 'business_revenue'
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($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-sandbox.circle.com/v1/payouts/{id}/rfi/{rfiId}/submit"

	payload := strings.NewReader("{\n  \"fields\": {\n    \"purposeOfFunds\": \"payroll\",\n    \"sourceOfFunds\": \"business_revenue\"\n  }\n}")

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

	req.Header.Add("Authorization", "Bearer <token>")
	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-sandbox.circle.com/v1/payouts/{id}/rfi/{rfiId}/submit")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"fields\": {\n    \"purposeOfFunds\": \"payroll\",\n    \"sourceOfFunds\": \"business_revenue\"\n  }\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api-sandbox.circle.com/v1/payouts/{id}/rfi/{rfiId}/submit")

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

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"fields\": {\n    \"purposeOfFunds\": \"payroll\",\n    \"sourceOfFunds\": \"business_revenue\"\n  }\n}"

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

{
  "data": {
    "id": "b8627ae8-732b-4d25-b947-1df8f4007a29",
    "paymentId": "f4b26b87-0000-4c42-a8d6-000000000001",
    "status": "IN_REVIEW",
    "level": "LEVEL_1",
    "expiresAt": "2020-04-17T02:13:30.000Z",
    "fieldRequirements": {
      "version": 1,
      "schema": {
        "type": "object",
        "required": [
          "purposeOfFunds"
        ],
        "properties": {
          "purposeOfFunds": {
            "type": "string"
          }
        }
      }
    },
    "fileRequirements": []
  }
}

{
  "code": 400,
  "message": "Bad request."
}

{
  "code": 401,
  "message": "Malformed authorization."
}

{
  "code": 404,
  "message": "Not found."
}