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/9` is listed as "Premium API Access" and costs up to $0.02 per request (20,000 base units of USDC with 6 decimals). Payment is handled via the x402 protocol — no API keys, accounts, or rate limits are required; callers simply attach an X-PAYMENT header with a valid payment proof.
The broader 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 endpoints are listed at the same $0.02/request price point.
However, the specific functionality of the `/api/v1/inbox/9` endpoint is unclear. The path pattern ("inbox/9") does not correspond to any of the documented API categories on the landing page, and the description is simply "Premium API Access" with no further detail on what data or service it returns. There is no OpenAPI spec, no request/response schema documentation, and the crawled sub-pages (/api, /pricing, /README) returned only a "Connect wallet" prompt with no additional content. Callers should be aware that the actual behavior of this endpoint is undocumented.
Capabilities
Use cases
- —Programmatic access to a pay-per-call API without needing API keys or subscriptions
- —Agent-driven workflows that need to pay for API calls on-the-fly using USDC on Base
- —Testing x402 payment flows against a live endpoint
Fit
Best for
- —Developers or agents wanting frictionless pay-per-request API access
- —x402 protocol integrators looking for low-cost test endpoints
- —Users who prefer crypto-native micropayments over traditional API billing
Not for
- —Users who need well-documented endpoint schemas and guaranteed SLAs
- —Anyone requiring free or subscription-based API access without per-call crypto payments
- —Production workloads that depend on understanding exact request/response contracts
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/9 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>" \
-d '{}'Endpoint
Quality
The endpoint is live (returns a valid 402 x402 challenge) and pricing is clear ($0.02 USDC on Base), but the specific endpoint /api/v1/inbox/9 has no documented purpose, no request/response schema, no OpenAPI spec, and the crawled pages beyond the landing page are empty. The "inbox/9" path doesn't match any advertised API category, making this effectively a stub listing.
Warnings
- —The /api/v1/inbox/9 endpoint path does not match any of the documented API categories on the landing page — its actual functionality is unknown.
- —No OpenAPI specification, request schema, or response schema is available for any endpoint.
- —Crawled sub-pages (/api, /pricing, /README) returned only 'Connect wallet' with no documentation content.
- —The platform appears to be a generic x402 demo or early-stage project; endpoint reliability and data quality are unverified.
Citations
- —The endpoint returns a 402 x402 challenge with maxAmountRequired of 20000 base units of USDC on Base networkhttps://lowpaymentfee.com/api/v1/inbox/9
- —All listed endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —The platform offers endpoints in four categories: Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructurehttps://lowpaymentfee.com
- —USDC asset address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/inbox/9