Pay-per-call API platform on Base (USDC) offering data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-enabled API platform that provides a broad catalog of pay-per-request endpoints settled in USDC on the Base network. The specific endpoint at `/api/v1/inbox/100` is listed as "Premium API Access" and costs up to $0.02 per call (20,000 base units of USDC with 6 decimals). Payment is handled via the x402 protocol — no API keys, no subscriptions, no rate limits. Callers attach an `X-PAYMENT` header with a valid payment proof and receive the response immediately.
The wider platform advertises four endpoint 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 functionality of the `/api/v1/inbox/100` endpoint is not documented beyond its title "Premium API Access." There is no OpenAPI schema, no request/response examples, and the crawled docs pages (pricing, README, API) returned only a "Connect wallet" prompt with no additional content. The endpoint is live and returns a well-formed x402 challenge, but what it actually returns upon successful payment is unknown.
Capabilities
Use cases
- —Programmatic access to a pay-per-call API without needing API keys or subscriptions
- —Agent-driven workflows that settle per-request costs in USDC on Base
- —Accessing data, AI inference, finance, or utility endpoints with micropayments
Fit
Best for
- —Developers wanting zero-commitment, pay-as-you-go API access
- —AI agents with x402-compatible payment capabilities
- —Users who prefer crypto-native (USDC on Base) billing over traditional subscriptions
Not for
- —Users who need detailed API documentation or OpenAPI specs before integrating
- —Applications requiring guaranteed SLAs or enterprise support
- —Users without USDC on Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/100 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>"Endpoint
Quality
The endpoint is live and returns a valid x402 challenge, but there is zero documentation on what /api/v1/inbox/100 actually does or returns. No OpenAPI schema, no request/response examples, and the crawled pages beyond the homepage were empty. The listing is effectively a stub with confirmed liveness.
Warnings
- —No documentation exists for the /api/v1/inbox/100 endpoint beyond its title 'Premium API Access'
- —No OpenAPI schema or request/response examples available
- —Crawled docs, pricing, and README pages returned no useful content (only 'Connect wallet')
- —The actual functionality and response format of this endpoint are completely unknown
Citations
- —The endpoint returns a valid x402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/inbox/100
- —The platform lists endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories, all at $0.02/requesthttps://lowpaymentfee.com
- —Pricing is $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —USDC asset address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/inbox/100