curl --request POST \
  --url https://api.grailpay.com/3p/api/v1/bank-account/{user_uuid} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "plaid": {
    "access_token": "access-token",
    "account_id": "account-id"
  },
  "custom": {
    "account_number": "12345678901234567",
    "routing_number": 123456789,
    "account_name": "John Doe",
    "account_type": "checking",
    "validate_account_routing": true
  },
  "billing_merchant_user_uuid": "a1b2c3d4-e5f6-g7h8-i9j0-k1l2m3n4o5p6",
  "billing_processor_mid": "1213121313"
}
'

import requests

url = "https://api.grailpay.com/3p/api/v1/bank-account/{user_uuid}"

payload = {
    "plaid": {
        "access_token": "access-token",
        "account_id": "account-id"
    },
    "custom": {
        "account_number": "12345678901234567",
        "routing_number": 123456789,
        "account_name": "John Doe",
        "account_type": "checking",
        "validate_account_routing": True
    },
    "billing_merchant_user_uuid": "a1b2c3d4-e5f6-g7h8-i9j0-k1l2m3n4o5p6",
    "billing_processor_mid": "1213121313"
}
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({
    plaid: {access_token: 'access-token', account_id: 'account-id'},
    custom: {
      account_number: '12345678901234567',
      routing_number: 123456789,
      account_name: 'John Doe',
      account_type: 'checking',
      validate_account_routing: true
    },
    billing_merchant_user_uuid: 'a1b2c3d4-e5f6-g7h8-i9j0-k1l2m3n4o5p6',
    billing_processor_mid: '1213121313'
  })
};

fetch('https://api.grailpay.com/3p/api/v1/bank-account/{user_uuid}', 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.grailpay.com/3p/api/v1/bank-account/{user_uuid}",
  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([
    'plaid' => [
        'access_token' => 'access-token',
        'account_id' => 'account-id'
    ],
    'custom' => [
        'account_number' => '12345678901234567',
        'routing_number' => 123456789,
        'account_name' => 'John Doe',
        'account_type' => 'checking',
        'validate_account_routing' => true
    ],
    'billing_merchant_user_uuid' => 'a1b2c3d4-e5f6-g7h8-i9j0-k1l2m3n4o5p6',
    'billing_processor_mid' => '1213121313'
  ]),
  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.grailpay.com/3p/api/v1/bank-account/{user_uuid}"

	payload := strings.NewReader("{\n  \"plaid\": {\n    \"access_token\": \"access-token\",\n    \"account_id\": \"account-id\"\n  },\n  \"custom\": {\n    \"account_number\": \"12345678901234567\",\n    \"routing_number\": 123456789,\n    \"account_name\": \"John Doe\",\n    \"account_type\": \"checking\",\n    \"validate_account_routing\": true\n  },\n  \"billing_merchant_user_uuid\": \"a1b2c3d4-e5f6-g7h8-i9j0-k1l2m3n4o5p6\",\n  \"billing_processor_mid\": \"1213121313\"\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.grailpay.com/3p/api/v1/bank-account/{user_uuid}")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"plaid\": {\n    \"access_token\": \"access-token\",\n    \"account_id\": \"account-id\"\n  },\n  \"custom\": {\n    \"account_number\": \"12345678901234567\",\n    \"routing_number\": 123456789,\n    \"account_name\": \"John Doe\",\n    \"account_type\": \"checking\",\n    \"validate_account_routing\": true\n  },\n  \"billing_merchant_user_uuid\": \"a1b2c3d4-e5f6-g7h8-i9j0-k1l2m3n4o5p6\",\n  \"billing_processor_mid\": \"1213121313\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.grailpay.com/3p/api/v1/bank-account/{user_uuid}")

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  \"plaid\": {\n    \"access_token\": \"access-token\",\n    \"account_id\": \"account-id\"\n  },\n  \"custom\": {\n    \"account_number\": \"12345678901234567\",\n    \"routing_number\": 123456789,\n    \"account_name\": \"John Doe\",\n    \"account_type\": \"checking\",\n    \"validate_account_routing\": true\n  },\n  \"billing_merchant_user_uuid\": \"a1b2c3d4-e5f6-g7h8-i9j0-k1l2m3n4o5p6\",\n  \"billing_processor_mid\": \"1213121313\"\n}"

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

{
  "status": true,
  "message": "Bank account has been added.",
  "data": {
    "uuid": "b1b9b3b0-0b3b-4b3b-8b3b-0b3b3b3b3b3b",
    "account_number": "1234567890",
    "routing_number": "123456789",
    "account_name": "John Doe",
    "account_type": "checking",
    "aggregator_type": "plaid",
    "created_at": "2021-10-01 00:00:00",
    "is_default": true
  },
  "errors": null,
  "error_code": null
}

{
  "status": false,
  "message": "Invalid routing_number: 000000001. This routing number has an invalid check digit.",
  "data": null,
  "errors": null,
  "error_code": null
}

{
  "status": false,
  "message": "Invalid Token",
  "data": null,
  "errors": null,
  "error_code": null
}

{
  "status": false,
  "message": "User not found.",
  "data": null,
  "errors": null,
  "error_code": null
}

{
  "status": false,
  "message": "The requested billing merchant user uuid does not exist.",
  "data": null,
  "errors": null,
  "error_code": null
}

{
  "status": false,
  "message": "The given data was invalid.",
  "data": null,
  "errors": {
    "first_name": [
      "The account number is required."
    ]
  },
  "error_code": null
}