Neckr0ik X402 Payments

x402 payment protocol for AI agents. Enables autonomous micropayments using HTTP 402 status codes and stablecoins. Use when you need to pay for API access, accept payments for your services, or interact with x402-enabled endpoints.

x402 Payments for AI Agents

Autonomous payment protocol for AI agents using HTTP 402 + stablecoins.

What is x402?

x402 is an open standard for internet-native payments. It enables AI agents to pay for API calls automatically using stablecoins, without accounts or human intervention.

How it works:

1. Agent requests API endpoint
2. Server responds with HTTP 402 + payment details
3. Agent signs payment authorization
4. Payment settled on blockchain
5. Request fulfilled automatically

Key benefits:

• No accounts or API keys
• Instant settlement
• Micropayments per request
• Blockchain-agnostic (EVM + Solana)
• Perfect for autonomous agents

Quick Start

Check if endpoint supports x402

bash

neckr0ik-x402-payments check https://api.example.com/premium

Pay for API access

bash

neckr0ik-x402-payments pay https://api.example.com/premium --amount 0.01

Accept payments (for your API)

bash

neckr0ik-x402-payments serve --port 8080 --price 0.01

Payment Flow

text

Agent                x402 Facilitator           API Server
  |                        |                        |
  |-- GET /premium ------>|----------------------->|
  |                        |                        |
  |<-- HTTP 402 -----------|------------------------|
  |    (payment required)  |                        |
  |    {amount, address,   |                        |
  |     chain, facilitator}|                        |
  |                        |                        |
  |-- Sign payment ------>|                        |
  |                        |                        |
  |                        |-- Submit to chain --->|
  |                        |                        |
  |                        |<-- Confirmation ------|
  |                        |                        |
  |-- GET /premium --------|----------------------->|
  |    PAYMENT-SIGNATURE   |                        |
  |                        |                        |
  |<-- 200 OK -------------|------------------------|
  |    (data)              |                        |

Supported Chains

• Ethereum (Mainnet, L2s)
• Polygon
• Base
• Arbitrum
• Optimism
• Solana

Supported Stablecoins

• USDC
• USDT
• DAI

Commands

check

Check if an endpoint supports x402 payments.

bash

neckr0ik-x402-payments check <url>

Options:
  --timeout <ms>    Request timeout (default: 10000)

pay

Pay for API access and receive data.

bash

neckr0ik-x402-payments pay <url> [options]

Options:
  --amount <amount>    Maximum amount to pay (in USD)
  --chain <chain>      Preferred chain (default: base)
  --token <token>      Stablecoin token (default: usdc)
  --wallet <address>   Wallet to use for payment
  --dry-run            Show payment details without paying

serve

Start an x402-enabled API server.

bash

neckr0ik-x402-payments serve [options]

Options:
  --port <port>        Server port (default: 8080)
  --price <amount>     Price per request (in USD)
  --chain <chain>      Accept payments on chain (default: base)
  --token <token>      Accept stablecoin (default: usdc)
  --wallet <address>   Receiving wallet address

balance

Check your payment wallet balance.

bash

neckr0ik-x402-payments balance [options]

Options:
  --chain <chain>      Chain to check (default: all)

history

View payment history.

bash

neckr0ik-x402-payments history [options]

Options:
  --limit <n>         Number of transactions (default: 10)
  --chain <chain>      Filter by chain

Configuration

Set up your wallet for payments:

bash

# Set wallet private key (stored securely)
neckr0ik-x402-payments config set wallet.private_key <key>

# Or use environment variable
export X402_PRIVATE_KEY=<key>

# Set receiving address for payments
neckr0ik-x402-payments config set wallet.address <address>

Use Cases

As an Agent (Pay for API Access)

python

# Before: Need API key, account, subscription
response = requests.get("https://api.example.com/data", 
    headers={"Authorization": "Bearer YOUR_API_KEY"})

# After: Autonomous payment, no account needed
response = x402.get("https://api.example.com/data")

As a Provider (Accept Payments)

python

from x402 import PaymentMiddleware

app = Flask(__name__)
app.wsgi_app = PaymentMiddleware(app.wsgi_app, price=0.01)

@app.route("/premium-data")
def premium_data():
    return {"data": "only accessible after payment"}

# Requests to /premium-data automatically require payment

Security

• Private keys never leave your machine
• Payments signed locally
• Transaction broadcast through facilitators
• All settlements verified on-chain
• Payment receipts stored for audit

See Also

• references/x402-spec.md — Full protocol specification
• references/facilitators.md — List of known facilitators
• scripts/x402.py — Payment implementation