# GPT55 Prepaid Balance Top-Up

> GPT55 Prepaid Balance Top-Up is a paid API for AI agents from gpt55.558686.xyz, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-14).

Tops up a prepaid USDC balance account for use with the balance-metered GPT-5.5 chat completions endpoint, accepting $0.005 via x402 USDC payment on Base.

## Facts

- Endpoint: POST https://gpt55.558686.xyz/v1/wallet/topup
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/gpt55-prepaid-balance-top-up-e4d9e44a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_KkH-6C3E_YatSkzyMpjCQ

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability gpt55-prepaid-balance-top-up-e4d9e44a -d '<json body>'
```

Example prompt: Top up my GPT55 balance account (account ID 'acct_abc123') with $0.005 USDC so I can keep using the balance-metered chat completions endpoint.

## When to prefer this

Use this endpoint when you need to pre-fund a balance account before making repeated calls to the gpt55.558686.xyz balance-metered chat completions endpoint, and want to pay once via x402 USDC on Base rather than paying per individual chat request.

## Known failure modes

- Payment not received or incorrect USDC amount sent — top-up not applied
- Invalid or missing accountId — account not found or created
- x402 payment protocol error — transaction rejected on Base network
- Duplicate requestId — idempotency conflict or replay rejection
- Insufficient USDC in sender wallet — payment fails before credit

## How this service works

Prepaid GPT55 balance top-up for the balance-metered chat endpoint. Pay $0.005 with x402 exact USDC on Base, then use the returned balance account token at /v1/chat/completions/balance.

## Output

Returns a balance account token that can be used as authentication for the /v1/chat/completions/balance endpoint, along with confirmation of the credited balance amount.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "topupUsd": {
   "type": "number",
   "minimum": 0
  },
  "accountId": {
   "type": "string",
   "maxLength": 120,
   "minLength": 1
  },
  "requestId": {
   "type": "string",
   "maxLength": 160
  },
  "topup_usd": {
   "type": "number",
   "minimum": 0
  },
  "account_id": {
   "type": "string",
   "maxLength": 120,
   "minLength": 1
  },
  "request_id": {
   "type": "string",
   "maxLength": 160
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/gpt55-prepaid-balance-top-up-e4d9e44a/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from gpt55.558686.xyz](https://www.zero.xyz/host/gpt55.558686.xyz/llms.txt)