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 platform that offers a broad catalog of pay-per-request 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 via the x402 protocol.
The specific endpoint at `/api/v1/invoices/4` is listed as "Premium API Access" and its x402 challenge advertises a maxAmountRequired of 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02 given USDC's 6 decimals. Payment is made via the `exact` scheme with a 300-second timeout. No API keys or rate limits are required — callers simply attach an X-PAYMENT header to each request.
Documentation is extremely sparse. The docs, API, pricing, and README pages all render only a "Connect wallet" prompt with no substantive content. There is no OpenAPI schema, no request/response examples, and no detailed description of what the `/api/v1/invoices/4` endpoint actually returns. The platform's landing page lists many endpoints but provides no technical documentation for any of them. The endpoint is live (returns a valid 402 challenge), but the actual functionality behind this specific invoice endpoint is unclear.
Capabilities
Use cases
- —Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API key management
- —Fetching real-time financial data such as exchange rates, token quotes, and gas estimates on a per-call basis
- —Running data analytics queries and exporting data with per-request billing
- —Using utility services like geocoding, validation, and conversion via micropayments
Fit
Best for
- —Agents and developers who want keyless, pay-per-use API access
- —Use cases requiring low-friction micropayments on Base/USDC
- —Prototyping and low-volume usage where subscription plans are overkill
Not for
- —High-volume production workloads needing guaranteed SLAs and detailed documentation
- —Users who need well-documented request/response schemas before integrating
- —Teams that cannot transact in USDC on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/4 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is live and returns a valid x402 402 challenge, but there is no OpenAPI schema, no request/response examples, and no meaningful documentation beyond the landing page listing. The actual purpose of the /api/v1/invoices/4 endpoint is unclear. Docs pages are empty (wallet-connect only). This is effectively a stub listing.
Warnings
- —No OpenAPI or schema documentation available for any endpoint
- —All documentation pages (docs, API, pricing, README) render only 'Connect wallet' with no content
- —The specific purpose and response format of /api/v1/invoices/4 is undocumented
- —The platform lists many endpoints but none have detailed technical docs
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 for /api/v1/invoices/4 specifies maxAmountRequired of 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Basehttps://lowpaymentfee.com/api/v1/invoices/4
- —Available API categories include Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructurehttps://lowpaymentfee.com
- —Docs, API, pricing, and README pages contain only a 'Connect wallet' prompthttps://lowpaymentfee.com/docs