topup_balance
Top up the prepaid balance with USDC. Auth required. Payment flow: call once without x_payment — a 402 reply lists the exact EIP-3009 requirements (amount, USDC asset, recipient, EIP-712 domain). Sign a transferWithAuthorization for them outside MCP (this server cannot sign), then call again with x_payment set to the base64 of {x402Version:1, scheme:'exact', network, payload:{signature, authorization}}.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| x_payment | No | base64 X-PAYMENT value from a previously answered 402 (see description) | |
| amount_usd | Yes | top-up amount in USD, decimal string |