1. The point
Every send on TRON uses up a resource the network sells for TRX. So an app that moves USDT has to keep each of its users supplied with TRX as well, and a user who runs out is holding money they cannot move.
This API takes that away. You deposit USDT once, from an address you hold the key for. Each send after that is paid from the credit: we put the resource on the sending address, broadcast the transaction, and charge the credit. Your users see USDT going out and a fee in USDT. TRX never comes up.
2. What it costs
A send costs less with a credit than it does paid one at a time. The usual figures:
| Sending to | Prepaid | Per send, in the app | Saving |
|---|---|---|---|
| someone who already holds USDT | 1.50 USDT | 2.00 USDT | 25% |
| an address that has never held USDT | 2.00 USDT | 3.00 USDT | 33% |
The fee is worked out for each send from the network's price at that moment, and on most days it is exactly the figure above. Before anything is signed, the quote says what the send will take from the credit. We pay the network for the send and take that amount from the credit.
Your account shows the minimum deposit and where to send it. Credit is not refundable and does not expire.
3. How a send goes
Deposit. Your account says where to send and the least to send. Send it yourself and tell the API, or sign the transfer and hand it over: we pay the network for it and put it on the credit.
Ask the price. Where from, where to, how much. The answer is what the send will take from the credit.
Send. Your user signs the USDT transfer with their own key. You hand it over together with a signature from the deposit address, which is what lets the credit be charged. We put the resource on the sending address, broadcast, and follow the transaction to a block.
Read the result. The balance, and the list of what was charged and why, are a call away.
4. No account, no API key
Your account is an address you hold the key for, and every request is signed with that key. A wallet that keeps the key behind a fingerprint signs once for a read token, then shows the credit and the history without asking again. There is nothing to register, no secret to store on a server, and nothing of yours we could leak.
5. Build against it
The reference has every operation, with its parameters, the errors it can return, and a whole program for it in Node.js, Python and Java, signing included. The OpenAPI document is the same contract, ready for a client generator.
A client in one file, with every operation and the signing: Node.js with TronWeb, Python, or Java with web3j. Each is the code the reference shows, tested against the API on Nile.