# MCP Gateway API Key Top-Up

> MCP Gateway API Key Top-Up is a paid API for AI agents from discovery.hugen.tokyo, paid per call via x402, $1/call, status unknown (last checked 2026-09-14).

Credits $1.00 USD to an MCP Gateway API key balance via a $1.00 USDC payment, enabling the key to call 58 MCP Gateway tools without per-call wallet setup.

## Facts

- Endpoint: POST https://discovery.hugen.tokyo/keys/topup
- Price: $1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/discovery-hugen-tokyo-58f89c2a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_nKqt6W19klyTLKmqbOttU

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 discovery-hugen-tokyo-58f89c2a -d '<json body>'
```

Example prompt: Add $1 of credit to my MCP Gateway API key mgk_test_12345 so I can start using the DeFi and weather tools without setting up a wallet.

## When to prefer this

Use this endpoint when an AI agent or developer holds an MCP Gateway API key and needs to pre-fund it with USDC to unlock access to the 58 bundled tools (DeFi, Weather, Security, Domain, Intelligence, etc.) without integrating per-call wallet payment. Prefer this over direct x402 per-call payment when the agent will make multiple downstream tool calls and wants a simpler credential-based flow.

## Known failure modes

- Invalid or missing API key — key not recognized, no credit applied
- Payment failure — USDC transaction on Base not confirmed, balance unchanged
- Malformed request body — missing 'key' field returns validation error
- Insufficient funds in calling wallet — x402 payment rejected
- Network/gateway timeout — payment state unknown, may require idempotency check

## How this service works

Top up MCP Gateway API key balance — $1.00 USDC credited per call. API keys let agents use 58 MCP Gateway tools (DeFi, Weather, Security, Domain, Intel, etc.) without wallet setup. Create a free key at POST /keys/create, then top up here.

## Output

Returns a confirmation that $1.00 USD was credited to the specified API key, the new running balance (e.g. $1.05), a notice about the x402 payment on Base, and alternative access options including MCP server and broker endpoints.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "key"
 ],
 "properties": {
  "key": {
   "type": "string",
   "title": "Key",
   "description": "API key to top up"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/discovery-hugen-tokyo-58f89c2a/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from discovery.hugen.tokyo](https://www.zero.xyz/host/discovery.hugen.tokyo/llms.txt)