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

# x402 payments

> Return payment requirements through HTTP so agents can understand price, chain, asset, and retry behavior.

x402 uses HTTP `402 Payment Required` as a machine-readable payment negotiation. For The Spawn docs, the user-facing explanation is:

```text theme={null}
Charge for one tool call without forcing a subscription, API key, or account setup.
```

## First-run shape

1. Offer a demo request that needs no wallet.
2. Return `402` for unpaid paid requests.
3. Include exact payment requirements.
4. Let the caller retry after payment and receive a receipt.

## Verified unpaid response

```bash theme={null}
curl -i https://socialintel.dev/v1/search \
  -H "Content-Type: application/json" \
  --data '{"query":"yoga","country":"US","limit":1}'
```

Expected status:

```text theme={null}
HTTP/2 402
payment-required: <base64 x402 payload>
content-type: application/json
```

The verified payload included accepted Base USDC and Solana USDC payment options. The Base option used amount `500000`, which is `$0.50` for a 6-decimal USDC asset.

## What to expose

| Item     | Example                                                                                |
| -------- | -------------------------------------------------------------------------------------- |
| Network  | `eip155:8453` for Base                                                                 |
| Asset    | USDC contract address on Base, or the Solana USDC mint when the service accepts Solana |
| Amount   | `500000` for `$0.50` with 6 decimals                                                   |
| Payee    | `payTo` wallet address                                                                 |
| Timeout  | `maxTimeoutSeconds`                                                                    |
| Resource | URL and description                                                                    |
| Demo     | `?demo=true` or tool argument `demo: true`                                             |
| Schema   | input and output shape                                                                 |

## How agents should handle it

An agent should summarize price and payment state before any paid execution:

```text theme={null}
This call costs $0.50 USDC on Base. Your linked Spawn wallet has 0.00 USDC. Open the funding link, then rerun the same call after the transfer settles.
```

Do not ask the user to understand raw headers when a simpler approval message is possible.

## Next

* [Charge for tool calls](/paths/charge-for-tool-calls)
* [Wallet funding](/payments/wallet-funding)
* [Quality scoring](/quality/scoring)