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 `/api/v1/inbox/143` 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 signed 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.
The `/api/v1/inbox/143` endpoint itself has no public documentation beyond its title. There is no OpenAPI spec, no request/response schema, and no usage examples available from the crawled pages. The endpoint is confirmed live — it returns a valid x402 402 challenge with scheme "exact" on the Base network, paying to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` using USDC (`0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`). The method is POST and the response MIME type is `application/json`.
Capabilities
Use cases
- —Programmatic access to a premium API endpoint without needing API keys or subscriptions
- —Agent-driven workflows that need to pay per call using USDC on Base
- —Testing x402 payment flows against a live endpoint
Fit
Best for
- —Developers or agents wanting zero-signup, pay-per-use API access
- —x402 protocol integrators looking for live endpoints on Base
- —Scenarios requiring no rate limits and instant access
Not for
- —Users who need detailed API documentation or guaranteed SLAs before integrating
- —Anyone without USDC on the Base network or an x402-compatible client
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/143 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <signed-x402-payment-proof>" \
-d '{}'Endpoint
Quality
The endpoint is confirmed live with a valid x402 402 challenge, but there is no OpenAPI spec, no request/response schema, no documentation for what this specific endpoint does, and no examples. The 'Premium API Access' title is entirely generic. The broader site lists many endpoints but provides no detail on any of them.
Warnings
- —No OpenAPI or schema documentation available for this endpoint
- —The purpose of /api/v1/inbox/143 ('Premium API Access') is completely undocumented — it is unclear what data or service it provides
- —No request body schema or response schema is published
- —The /api, /pricing, and /README pages all returned only a 'Connect wallet' prompt with no useful content
- —Cannot verify what the endpoint actually returns upon successful payment
Citations
- —The endpoint returns a valid x402 402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/inbox/143
- —All listed endpoints cost $0.02 per request with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —The platform offers endpoints in Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com
- —USDC contract address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base networkhttps://lowpaymentfee.com/api/v1/inbox/143