> ## Documentation Index
> Fetch the complete documentation index at: https://docs.metalntwx.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Credits

> RPC is prepaid in USD and drawn down per request at a rate by method; top up with a card, or let an agent top up over x402

An [endpoint](https://docs.metalntwx.com/network/endpoints.md) draws on the account's credit, a USD
balance each request draws down at the rate for its method. There is no
subscription and no invoice.

| Class | Per 1,000 requests | Methods |
| - | - | - |
| Base | \$0.05 | Every other method, such as `eth_blockNumber`, `eth_getBalance`, `eth_getBlockByNumber` and `eth_sendRawTransaction` |
| Heavy | \$0.08 | `eth_call`, `eth_estimateGas`, `eth_getLogs`, `eth_getBlockReceipts` |
| Archive | \$0.20 | Reserved for archive history; no method uses it today |

A request is charged once it is answered, a JSON-RPC error from the chain
included.
A request the gateway refuses, or the chain fails to answer, costs nothing,
unless the chain received it and did not answer within 10 seconds: that is
charged, as a JSON-RPC error, since the chain may still be running it. The
console's Billing page shows the balance, and tops it up from the saved
card, by hand or whenever the balance falls below a threshold you set.

## Top up as an agent

With no credit, an endpoint answers `402`, an [x402](https://docs.metalntwx.com/agents/x402-on-metal.md)
challenge, so an agent holding `*USDZ` tops it up without a card. A payment
buys a credit pack of \$1:

```bash theme={null}
metal-agent pay https://rpc-testnet.metalntwx.com/v1/<endpoint id> --network testnet \
  --method POST --body '{"jsonrpc":"2.0","id":1,"method":"eth_blockNumber","params":[]}'
```

`GET` on the endpoint's URL returns the challenge, and paying it tops the
endpoint up without making a call, so an agent can top up before its credit
runs out:

```bash theme={null}
metal-agent pay https://rpc-testnet.metalntwx.com/v1/<endpoint id> --network testnet
```

An agent with no endpoint of yours
[buys its own](https://docs.metalntwx.com/network/endpoints.md#an-endpoint-for-your-agent) at the bare
`/v1`.

> [card] [Endpoints](https://docs.metalntwx.com/network/endpoints.md)
>
> Create an endpoint or let an agent buy one, authenticate it, and its limits.

> [card] [Pay for an API](https://docs.metalntwx.com/agents/quickstart-pay.md)
>
> The agent that pays a `402`, RPC included.


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