Metered API: consume x402 APIs with just an API key

We're introducing Metered API - a simpler way to consume x402 APIs without wallets, signatures, or crypto logic in your code.

Buyers authorize once, set a spending limit, then interact with APIs using a familiar API key flow. Payments are handled automatically, per request, in the background.

The problem

x402 is powerful, but for many developers the crypto side adds friction:

• You need a wallet connected
• Every request requires a payment signature
• You need to handle the x402 handshake in your code
• Managing private keys in a backend is a security concern

How Metered API works

1. Register in the RelAI dashboard and get an API key (starts with rpx_)
2. Fund your account - deposit USDC to your custodial wallet
3. Set spending limits - per transaction, daily, weekly, or monthly caps
4. Call any x402 API through the proxy using your API key

What it looks like in code

Before (with wallet + x402 SDK):

import { createX402Client } from '@relai-fi/x402/client';
const client = createX402Client({
  network: 'base',
  evmWallet: { address, signTypedData },
});
const response = await client.fetch('https://api.example.com/data');

After (with Metered API):

curl -X GET "https://relai.fi/api/metered/x?url=https://api.example.com/data" \
  -H "X-API-Key: rpx_your_api_key"

One header. One URL. No wallet. No signatures.

Built-in spending controls

Every API key comes with configurable limits:

• Per-transaction limit - cap the maximum amount per single API call
• Daily / weekly / monthly budget - set a rolling spending cap
• Usage dashboard - see exactly what you've spent, when, and on which APIs

Custodial wallets included

When you register, RelAI creates custodial wallets for you on every supported network:

• Solana - SPL USDC wallet
• Base, Polygon, Peaq, Sei - EVM USDC wallet

Who is this for?

• Backend developers who want to consume x402 APIs from their servers without managing wallets
• AI agents that need to call paid APIs autonomously
• Companies that want usage-based API access without crypto complexity
• Prototypers who want to test x402 APIs quickly without setting up wallet infrastructure

What stays the same for sellers

Nothing changes on the seller side. API providers still receive x402 payments as usual. The Metered API proxy is transparent - sellers don't know (or care) whether the buyer is using a wallet directly or going through the proxy.

Permissionless, usage-based payments stay intact.

Getting started

1. Go to the RelAI Dashboard
2. Open Metered API
3. Click Generate API Key
4. Fund your wallet with USDC
5. Start calling x402 APIs with your key