x402-gated API platform on Base offering data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-protocol API marketplace that gates access to a variety of endpoints behind per-request USDC micropayments on the Base network. The specific endpoint at `/api/v1/carts/47` is listed as "Premium API Access" and accepts POST requests with payment via the x402 exact scheme. The 402 challenge indicates a max amount of 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02 per request given USDC's 6 decimals.
The broader platform advertises four categories of APIs: 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 the same $0.02/request price point. The platform claims no API keys, no rate limits, and instant access — callers simply attach an x402 payment header to each request.
Documentation beyond the landing page is extremely sparse. The /docs, /api, /pricing, and /README pages all render only a "Connect wallet" prompt with no additional technical content. There is no OpenAPI spec, no request/response schema documentation, and no usage examples available from the crawl. The `/api/v1/carts/47` endpoint itself is live (returns a proper 402 challenge), but what it actually returns upon successful payment is unknown — the description simply says "Premium API Access" with a JSON mime type.
Capabilities
Use cases
- —Paying per-request for API access without API keys or subscriptions
- —Programmatic agent access to gated endpoints using x402 micropayments
- —Exploring x402 protocol integration with USDC on Base
Fit
Best for
- —Developers experimenting with x402 payment protocol
- —AI agents that need keyless, pay-per-call API access
- —Projects wanting low-friction micropayment-gated endpoints
Not for
- —Production workloads requiring documented request/response schemas
- —Users who need detailed API documentation or SDKs
- —Anyone without a Base-network USDC wallet
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/carts/47 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is live and returns a valid x402 402 challenge, confirming it works. However, there is no OpenAPI spec, no request/response schema, no documentation beyond a landing page, and the specific purpose of /api/v1/carts/47 is unclear. The docs, pricing, and README pages are all empty wallet-connect stubs.
Warnings
- —No OpenAPI or schema documentation available
- —All documentation pages (/docs, /api, /pricing, /README) return only a 'Connect wallet' prompt with no content
- —The specific purpose and response format of /api/v1/carts/47 ('Premium API Access') is undocumented
- —Cannot verify what data or service is actually delivered upon payment
Citations
- —The endpoint returns a 402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/carts/47
- —The platform lists APIs across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories all at $0.02/requesthttps://lowpaymentfee.com
- —The platform claims no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/carts/47