Pay-per-request API platform on Base network via x402 — $0.02/call in USDC.
What it does
lowpaymentfee.com is an x402-enabled API platform that offers a broad catalog of endpoints spanning data analytics, AI/ML inference, finance/Web3 data, and utility services. Every endpoint costs $0.02 per request, paid in USDC on the Base network with no API keys, no rate limits, and no commitments required. The x402 payment challenge is handled inline: callers attach an X-PAYMENT header to settle each request on-chain.
The specific endpoint at `/api/v1/carts/50` is listed as "Premium API Access" and returns a 402 challenge requesting up to 20,000 base units of USDC (0x8335…2913 on Base, 6 decimals = $0.02). The payment scheme is "exact" with a 300-second timeout, settling to address 0x1A2B…85F3. The endpoint accepts HTTP POST and returns application/json.
While the landing page advertises many endpoint categories (sentiment analysis, text summarization, embeddings, price feeds, gas estimates, geocoding, etc.), the crawled documentation pages were essentially empty (showing only a "Connect wallet" prompt). No OpenAPI spec, request/response schemas, or usage examples were found. The actual functionality behind `/api/v1/carts/50` is unclear — the name suggests a shopping cart resource but the description is generic. Treat this as a live but under-documented endpoint.
Capabilities
Use cases
- —Programmatic access to paid API endpoints without traditional API key management
- —Agent-driven workflows that need on-chain per-call payment settlement
- —Exploring x402 protocol integration for pay-as-you-go services
Fit
Best for
- —Developers experimenting with x402 payment protocol on Base
- —AI agents that can autonomously pay for API calls in USDC
- —Use cases requiring keyless, commitment-free API access
Not for
- —Production workloads requiring detailed API documentation and SLAs
- —Users without USDC on the Base network
- —High-volume use cases where per-call crypto settlement overhead is impractical
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/carts/50 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is live (402 challenge confirmed) and pricing is clear ($0.02 USDC on Base), but documentation is essentially nonexistent — all doc/pricing/API pages render only a wallet-connect prompt. No OpenAPI spec, no request/response schemas, and the specific purpose of /api/v1/carts/50 is unclear beyond the generic 'Premium API Access' label.
Warnings
- —Documentation pages are empty (only show 'Connect wallet' prompt) — no request/response schemas available
- —The purpose of /api/v1/carts/50 is unclear; 'Premium API Access' is a generic label with no specifics
- —No OpenAPI specification or example payloads found
- —The broader catalog of endpoints (AI, analytics, finance, utils) is advertised but none were individually verified
Citations
- —Endpoint returns 402 with x402 challenge requesting 20000 base units of USDC on Base networkhttps://lowpaymentfee.com/api/v1/carts/50
- —Platform advertises $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/carts/50
- —Platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com