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/13` is listed as "Premium API Access" and costs up to $0.02 per request (20,000 base units of USDC with 6 decimals). No API keys, rate limits, or upfront commitments are required — callers simply attach an x402 payment header to each POST request.
The platform advertises four categories of APIs: 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 x402 challenge was successfully captured with version 1 of the protocol, confirming the endpoint is live.
Notably, the specific `/api/v1/inbox/13` endpoint does not correspond to any of the named API categories on the landing page. Its purpose is unclear — it may be a generic inbox or message-passing endpoint. No OpenAPI schema, request/response examples, or detailed documentation were found during the crawl; the /api, /pricing, and /README pages all returned only a "Connect wallet" prompt with no substantive content.
Capabilities
Use cases
- —Programmatic access to utility or data endpoints without needing API key registration
- —Agent-driven workflows that pay per call using USDC on Base
- —Testing x402 payment flows against a live endpoint
Fit
Best for
- —Developers exploring x402 payment protocol integrations
- —AI agents needing keyless, pay-per-use API access
- —Low-volume consumers who want no subscription commitment
Not for
- —Users needing detailed API documentation or guaranteed SLAs
- —High-volume production workloads where $0.02/request adds up quickly
- —Anyone who needs to understand exactly what /api/v1/inbox/13 returns before paying
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/13 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>" \
-d '{}'Endpoint
Quality
The x402 challenge is live and pricing is clear ($0.02 USDC on Base), but there is no OpenAPI schema, no request/response examples, no documentation beyond a landing page listing, and the specific endpoint /api/v1/inbox/13 has no description of its actual functionality. The /api, /pricing, and /README pages returned no useful content.
Warnings
- —The endpoint /api/v1/inbox/13 does not match any named API on the provider's landing page — its actual functionality is unknown.
- —No OpenAPI spec, request schema, or response schema available.
- —No documentation pages returned substantive content (all showed only 'Connect wallet').
- —The 'Premium API Access' description is generic and does not explain what this endpoint does.
Citations
- —The x402 challenge returns maxAmountRequired of 20000 in USDC (asset 0x8335…) on Base, equaling $0.02 per request.https://lowpaymentfee.com/api/v1/inbox/13
- —The platform advertises $0.02/request pricing with no API keys, no rate limits, and instant access on the Base network.https://lowpaymentfee.com
- —Four API categories are listed: Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructure.https://lowpaymentfee.com