# Credit and billing

API credit is USDC you set aside on the ledger for your requests. Usage is counted as requests finish and charged once a day in one public transaction, which also pays the Macs.

## API credit

API credit is USDC from your MLX Wallet, held in the protocol account `api.mlx` for your requests. It shows on your account as `apiCredit`.

- **Add it** with the user transaction `api_fund` `{amount}`: at least 1 USDC, and at most 1,000 USDC of credit per wallet in the pilot. The [console](/console) signs it for you.
- **Take it back** with `api_refund` `{amount}`. You can take back credit that isn't paying for requests since the last bill or for requests running now; the console shows how much that is.
- `api.mlx` takes no transfers: a `transfer` to it fails, so USDC can't land there by mistake.

Your **available** credit is your credit, less what you've used since the last bill and the most your running requests could cost. A request is refused (402) when its most possible cost is more than that.

## Prices

$0.02 per million tokens, the prompt's and the completion's alike: $0.00002 per thousand. Usage is counted in billionths of a dollar as each request finishes and charged in whole millionths (USDC's base unit), rounded down.

## The daily bill

After 00:10 UTC each day the sequencer sends one system transaction, `compute_bill`. Every figure in it is a running total since the pilot started, so only what's new moves and sending the same bill twice moves nothing:

| Field | What the ledger does |
| --- | --- |
| `charges[]` `{account, billed}` | Takes `billed − apiBilled` from that wallet's API credit (never more than the credit holds) and records `apiBilled = billed`. |
| `pays[]` `{account, earned}` | Pays `earned − apiEarned` in USDC from what was charged to that wallet (a Mac's owner), never locked. A pay the day's charges can't cover yet stays due for the next bill. |
| `fee` | Moves `fee` less what was already sent to `treasury.mlx`. |

`api.mlx` always holds exactly the wallets' API credit plus what was charged and not yet paid out. The explorer shows each bill and each wallet's line in it.

```endpoint try
GET /api/account/api.mlx
```

## Who gets what

For each request, 90% of its price is split equally between the wallets of the Macs whose answer was returned (two, when it was checked), and 10% is the network's fee, sent to the treasury. The whitepaper's split is 85% to the worker, 5% to the verifier and 10% to the protocol. In the pilot both Macs do the whole job, so the worker's and the verifier's shares are split equally between them.