x402 Protocol
402.cat uses x402 micropayment protocol instead of API keys. Pay per request with USDC.Payment Flow
1
Request
Make request to protected endpoint
2
402 Response
Server returns
HTTP 402 Payment Required with payment details3
Sign
Create EIP-3009 authorization signature
4
Retry
Retry request with
PAYMENT-SIGNATURE headerHeaders
V2 (Current):Using httpcat-cli
CLI handles authentication automatically:Manual Implementation
See x402 Protocol for detailed implementation guide.Referrals
Add referrer header to earn 10% of fees:x402 Protocol Details
Complete x402 documentation