Pay-per-call API platform on Base (USDC) covering data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-enabled API platform that offers a broad catalog of pay-per-request endpoints settled in USDC on the Base network. The specific endpoint at `/api/v1/invoices/46` 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 site organizes its APIs into 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 listed endpoints share the same $0.02/request pricing. However, the specific endpoint being listed here (`/api/v1/invoices/46`) is labeled generically as "Premium API Access" and does not appear in the site's public catalog, so its exact functionality is unclear.
Documentation is extremely thin — the /docs, /api, /pricing, and /README pages all render only a "Connect wallet" prompt with no further content. There is no OpenAPI spec, no request/response schema documentation, and no usage examples available from the crawled material. The endpoint is confirmed live (402 challenge captured), but what it actually returns upon successful payment is unknown.
Capabilities
Use cases
- —Programmatic access to data analytics and reporting endpoints without API key management
- —AI inference tasks (sentiment analysis, summarization, classification, embeddings) paid per request
- —Fetching real-time financial data such as exchange rates, token quotes, and gas estimates
- —Utility operations like geocoding, validation, and data conversion
Fit
Best for
- —Agents or bots that need keyless, pay-as-you-go API access
- —Developers wanting to avoid subscription commitments for occasional API calls
- —x402-compatible clients on the Base network looking for low-cost endpoints
Not for
- —Users who need detailed API documentation or OpenAPI specs before integrating
- —High-volume consumers who would benefit from bulk pricing or subscriptions
- —Anyone without a Base-network USDC wallet or x402-compatible client
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/46 \
-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 the specific functionality of /api/v1/invoices/46 is undocumented and does not appear in the site's public catalog. Documentation pages are empty (wallet-connect only), there is no OpenAPI spec, no request/response examples, and no schema beyond the x402 challenge. Effectively a stub listing.
Warnings
- —The endpoint /api/v1/invoices/46 is not listed in the site's public API catalog — its actual functionality is unknown
- —All documentation pages (/docs, /api, /pricing, /README) render only a 'Connect wallet' prompt with no usable content
- —No OpenAPI spec, request schema, or response schema is available
- —The platform's breadth of advertised endpoints (AI, finance, data, utils) cannot be verified from crawl data
Citations
- —The x402 challenge requests maxAmountRequired of 20,000 base units of USDC (USD Coin) on Base networkhttps://lowpaymentfee.com/api/v1/invoices/46
- —The site advertises $0.02/request pricing with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —The platform lists endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com
- —Documentation pages render only a Connect wallet prompthttps://lowpaymentfee.com/docs