`wallet` is the read-only fourth control tool. It answers whether the account can afford a new run and explains what is currently reserved.

## Signature

```text
wallet({})
```

```json
{
  "name": "wallet",
  "arguments": {}
}
```

The input object has no fields. Adding funds and changing the confirmation threshold are human actions on the web wallet.

## Return shape

The response includes settled `balance`, `held` funds from in-flight runs, `available` spend, `confirm_threshold`, recent ledger entries and a `topup_url`. It also includes a display block for values shown to a human.

```json
{
  "balance": "<USD decimal string>",
  "held": "<USD decimal string>",
  "available": "<balance minus held>",
  "confirm_threshold": "<USD decimal string>",
  "topup_url": "https://scrollport.com/wallet/topup"
}
```

Use `available` for affordability. Do not subtract a second time or assume that settled balance is free to spend while another run is in flight.

## Security and money behavior

The wallet tool is read-only by design. An agent that could raise its own spending threshold or add a card would turn prompt injection into a money-control path. A run still performs the hold → capture or release sequence; `wallet` only reports it.

For the full ledger model, read [wallet and spending](https://scrollport.com/docs/guides/wallet). To begin an execution, continue to [discover](https://scrollport.com/docs/control-tools/discover).