Pay-per-call API platform on Base via x402 — data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-enabled API marketplace that offers a variety of 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 priced at $0.02 per request, paid in USDC on the Base network.
The specific endpoint at `/api/v1/invoices/33` is listed as "Premium API Access" and returns a 402 challenge requesting up to 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02. Payment uses the x402 "exact" scheme with a 300-second timeout. No API keys or rate limits are advertised — access is gated entirely by the x402 payment header.
Documentation is extremely sparse. The docs, API, pricing, and README pages all render only a "Connect wallet" prompt with no further content. There is no OpenAPI schema, no request/response examples, and no detailed documentation for any endpoint. The exact functionality behind `/api/v1/invoices/33` (labeled "Premium API Access") is unclear — it does not appear in the main endpoint listing on the homepage, so its purpose is ambiguous.
Capabilities
Use cases
- —Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API keys
- —Fetching real-time financial data like token quotes, gas estimates, and exchange rates
- —Running utility operations like geocoding, validation, and data conversion on a per-call basis
- —Integrating pay-per-use data analytics into agent workflows
Fit
Best for
- —Agents needing low-cost, no-signup API access via x402 on Base
- —Developers prototyping with multiple API categories without committing to subscriptions
- —Web3-native applications that prefer on-chain payment rails over traditional billing
Not for
- —Users who need detailed API documentation or OpenAPI schemas before integrating
- —High-volume production workloads where per-request crypto payments add overhead
- —Anyone requiring guaranteed SLAs or support contracts
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/33 \
-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, documentation is essentially nonexistent — all doc pages show only 'Connect wallet'. There is no OpenAPI schema, no request/response examples, and the specific purpose of /api/v1/invoices/33 is unclear since it doesn't appear in the homepage listing. The listing is effectively a stub with pricing info only.
Warnings
- —Documentation pages (/docs, /api, /pricing, /README) all render only 'Connect wallet' with no usable content
- —No OpenAPI or schema available for any endpoint
- —The endpoint /api/v1/invoices/33 ('Premium API Access') is not listed on the homepage — its specific functionality is unknown
- —No request or response examples are available anywhere in the crawled material
Citations
- —All endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —The x402 challenge requests maxAmountRequired of 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base, equaling $0.02https://lowpaymentfee.com/api/v1/invoices/33
- —Available API categories include Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructurehttps://lowpaymentfee.com
- —Docs, API, pricing, and README pages render only 'Connect wallet' with no further contenthttps://lowpaymentfee.com/docs