Pay-per-call API platform on Base with USDC payments via x402 — $0.02/request, no API keys required.
What it does
lowpaymentfee.com is an x402-enabled API platform that offers a broad catalog of pay-per-request endpoints across data analytics, AI/ML inference, finance/Web3, and infrastructure utilities. All endpoints are priced at $0.02 per request, settled in USDC on the Base network. The x402 protocol means no API keys, no accounts, and no rate limits — callers simply attach a payment header to each request.
The specific endpoint at `/api/v1/invoices/15` is listed as "Premium API Access" and returns a 402 challenge requesting up to 20,000 base units of USDC (0.02 USD, since USDC uses 6 decimals) on Base. The payment is made to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` using the "exact" payment scheme with a 300-second timeout.
The broader platform advertises endpoints for sentiment analysis, text summarization, classification, embeddings, price feeds, exchange rates, token quotes, gas estimates, geocoding, validation, conversion, and generation — all at the same $0.02 price point. However, documentation beyond the landing page is extremely sparse (docs, pricing, and API pages all render only a "Connect wallet" prompt), so the actual functionality, request/response schemas, and data sources behind these endpoints are unverified.
Capabilities
Use cases
- —Agents needing on-demand AI inference (sentiment, summarization, classification) without managing API keys
- —Fetching real-time crypto token quotes or gas estimates with per-call USDC micropayments
- —Geocoding or data validation as a utility service within automated workflows
- —Exporting analytics data or generating reports on a pay-as-you-go basis
Fit
Best for
- —Developers and agents wanting zero-signup, pay-per-use API access
- —Crypto-native applications that can settle in USDC on Base
- —Low-volume or bursty workloads where flat per-request pricing is economical
Not for
- —High-volume production workloads needing SLAs, rate guarantees, or dedicated support
- —Users who need detailed API documentation and well-defined schemas before integrating
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/15 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-header>"Endpoint
Quality
The endpoint is live and returns a valid x402 402 challenge, confirming it accepts USDC on Base at $0.02. However, there is no OpenAPI schema, no request/response examples, and all documentation pages beyond the landing page are empty ('Connect wallet' only). The actual functionality behind '/api/v1/invoices/15' is unclear — the name 'Premium API Access' is generic and uninformative.
Warnings
- —Documentation pages (/docs, /pricing, /api, /README) are all effectively empty, rendering only 'Connect wallet'
- —No OpenAPI or schema available — request and response formats are unknown
- —The specific endpoint '/api/v1/invoices/15' has a generic description; its actual functionality is unverified
- —The platform lists many endpoint categories but none could be independently verified for functionality
Citations
- —All endpoints priced at $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —x402 challenge returns maxAmountRequired of 20000 base units of USDC (0.02 USD) on Base with 300-second timeouthttps://lowpaymentfee.com/api/v1/invoices/15
- —Platform offers endpoints across Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com
- —USDC asset address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base networkhttps://lowpaymentfee.com/api/v1/invoices/15