x402-gated premium API endpoint on Base, pay-per-request with USDC.
What it does
This endpoint at `/api/v1/cards/11` is part of the lowpaymentfee.com platform, a collection of x402-protocol pay-per-call APIs spanning data analytics, AI/ML inference, finance/Web3, and infrastructure utilities. The specific `/api/v1/cards/11` endpoint is labeled "Premium API Access" but its exact functionality is not documented beyond that title. It accepts HTTP POST requests and returns JSON.
Payment is settled on the Base network using USDC (contract `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`). The maximum amount required per call is 20,000 base units of USDC, which with 6 decimals equals $0.02 USD per request. The platform advertises no API keys, no rate limits, and instant access — callers simply attach an x402 payment header to each request.
The broader lowpaymentfee.com platform offers roughly 16 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 (geocoding, validation, conversion, generation). All are priced at $0.02 per request. However, this specific listing is for `/api/v1/cards/11`, whose purpose is unclear from available documentation — it does not appear in the site's public API catalog.
Capabilities
Use cases
- —Accessing a premium API endpoint with per-request USDC micropayments
- —Integrating x402-protocol payment flows into agent workflows
- —Testing x402 payment challenges on Base network
Fit
Best for
- —Developers experimenting with x402 pay-per-call protocols
- —Agents that can settle USDC payments on Base
- —Use cases requiring no-signup, keyless API access
Not for
- —Users who need detailed documentation on what the endpoint returns
- —High-volume use cases where per-request crypto settlement adds latency
- —Anyone without a Base-compatible USDC wallet
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/cards/11 \
-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 the specific functionality of /api/v1/cards/11 is undocumented — it does not appear in the site's public API catalog. No request/response schema, no examples, and docs/pricing/README pages are all blank beyond a wallet-connect prompt.
Warnings
- —The endpoint /api/v1/cards/11 is not listed in the site's public API catalog; its actual functionality is unknown.
- —No request body schema or response schema is documented anywhere.
- —All documentation pages (docs, api, pricing, README) returned only a 'Connect wallet' prompt with no substantive content.
- —The purpose of 'Premium API Access' is entirely unclear — treat as a stub until more information is available.
Citations
- —The x402 challenge returns maxAmountRequired of 20000 base units of USDC on Base networkhttps://lowpaymentfee.com/api/v1/cards/11
- —USDC contract address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/cards/11
- —Platform advertises $0.02 per request, no API keys, no rate limits, instant accesshttps://lowpaymentfee.com
- —The site lists ~16 endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com