Building a UTXO Transaction

curl --location --request POST 'https://api.tatum.io/v3/bitcoin/transaction' \
--header 'x-api-key: {API_KEY}' \
--header 'Content-Type: application/json' \
--data-raw '{
    "fromAddress": [
        {
            "address": "address_1",
            "privateKey": "pk_address_1"
        }
    ],
    "to": [
        {
            "address": "address_1", //The rest of the coin gets defined to be sent back to the sender address.
            "value": 89.87654321 // Here you also consider the amount of "fee" you will allocate for the "miners"
        },
        {
            "address": "address_2", // where you want to transfer the 10BTC
            "value": 10
        }
    ]
  }'

// within the "to" IF you only have x1 address as destination and don't specify where the rest of the coins go, the blockchain considers that amount as the "fee" to be given to the miners!

curl --location --request POST 'https://api.tatum.io/v3/bitcoin/transaction' \
--header 'x-api-key: {API_KEY}' \
--header 'Content-Type: application/json' \
--data-raw '{
  "fromUTXO":[
      {
        "txHash":"######",
        "index":##, // the index of the "PublicAddress" within the "txHash"
        "privateKey":"pk_address_2"
      }
    ],
   "to": [ // this is an array, you can have multiple destinations
      {
        "address":"address_y", //main destination address
        "value":10
      }
    ],
  "changeAddress":"address_1", //where you sent the rest of "unspent" coin
  "fee":"0.87654321" // this fee is quite high for BTC or LTC, take it as an example.
}'