Pay-per-call API platform on Base with $0.02 USDC requests via x402 — no API keys required.
What it does
lowpaymentfee.com is a pay-per-request API platform that uses the x402 protocol to accept USDC payments on the Base network. The specific endpoint `/api/v1/invoices/37` is listed as "Premium API Access" and returns a 402 challenge requesting up to 20,000 base units of USDC (i.e., $0.02) per call. The platform advertises no API keys, no rate limits, and instant access — callers simply attach an X-PAYMENT header with a valid x402 payment proof.
The broader platform offers endpoints across four categories: Data & Analytics (metrics, reports, data export, insights), AI & Machine Learning (sentiment analysis, text summarization, classification, embeddings), Finance & Web3 (price feeds, exchange rates, token quotes, gas estimates), and Infrastructure utilities (geocoding, validation, conversion, generation). All endpoints are listed at $0.02 per request.
This particular endpoint (`/api/v1/invoices/37`) is labeled "Premium API Access" but no further documentation describes what data or functionality it returns. The docs, pricing, API, and README pages all render only a "Connect wallet" prompt with no additional content. Without schema details or response examples, the actual behavior of this endpoint remains unclear.
Capabilities
Use cases
- —Programmatic access to premium API data with per-call USDC micropayments
- —Agent-driven workflows that need keyless, on-demand API access
- —Testing x402 payment flows against a live endpoint on Base
Fit
Best for
- —Developers experimenting with x402 payment protocol
- —AI agents that can settle USDC payments on Base
- —Users who want pay-as-you-go access without subscriptions or API keys
Not for
- —Users who need detailed API documentation or response schemas before integrating
- —High-volume consumers who prefer flat-rate or subscription pricing
- —Anyone without a Base-compatible USDC wallet
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/37 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>"Endpoint
Quality
The endpoint is live and returns a valid x402 402 challenge, but there is no documentation, no OpenAPI schema, no response examples, and no description of what the endpoint actually returns. The docs/pricing/API pages are all blank beyond a wallet-connect prompt. The listing is effectively a stub.
Warnings
- —No documentation available — docs, pricing, API, and README pages all show only 'Connect wallet' with no content.
- —No OpenAPI or output schema provided; the actual response payload of /api/v1/invoices/37 is unknown.
- —The endpoint name 'Premium API Access' is generic and does not describe what data or functionality is returned.
- —Multiple other endpoints are advertised on the landing page but none have documented schemas or examples.
Citations
- —The endpoint returns a 402 challenge requesting up to 20,000 base units of USDC ($0.02) on Base network.https://lowpaymentfee.com/api/v1/invoices/37
- —The platform advertises $0.02 per request with no API keys, no rate limits, and instant access.https://lowpaymentfee.com
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913.https://lowpaymentfee.com/api/v1/invoices/37
- —The platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories.https://lowpaymentfee.com