Pay-per-request API platform on Base via x402 — data, AI, finance, and utility endpoints at $0.02/call.
What it does
lowpaymentfee.com is an x402-enabled API platform that offers a broad catalog of pay-per-request endpoints across four 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 priced at $0.02 per request, paid in USDC on the Base network.
The specific endpoint at `/api/v1/invoices/45` is listed as "Premium API Access" and returns a valid x402 challenge with a maxAmountRequired of 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02. Payment is made via the x402 exact scheme — no API keys, subscriptions, or rate limits are required. The endpoint accepts POST requests and returns application/json.
Documentation is extremely sparse: the /docs, /pricing, /api, and /README pages all render only a "Connect wallet" prompt with no further content. There is no OpenAPI spec, no request/response schema documentation, and no examples of what the `/api/v1/invoices/45` endpoint actually returns. The landing page lists many endpoints but provides no detail on input parameters or response formats for any of them. The endpoint is live (402 challenge confirmed), but without documentation it is unclear what data or functionality "Premium API Access" actually provides.
Capabilities
Use cases
- —Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API keys
- —Fetching real-time financial data like token quotes, gas estimates, and exchange rates
- —Running utility operations like geocoding, validation, and data conversion on a per-request basis
- —Programmatic data export and analytics retrieval with crypto micropayments
Fit
Best for
- —Agents or developers who want instant API access without signup or API key management
- —Low-volume or bursty workloads where pay-per-request is more economical than subscriptions
- —Web3-native applications that can settle payments in USDC on Base
Not for
- —High-volume production workloads where $0.02/request adds up quickly without bulk discounts
- —Users who need detailed API documentation, SLAs, or guaranteed uptime
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/45 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is live and returns a valid x402 challenge, confirming pricing and payment details. However, documentation is essentially nonexistent — all doc pages show only 'Connect wallet'. There is no OpenAPI spec, no request/response schema, and no explanation of what '/api/v1/invoices/45' actually returns. The listing is effectively a stub with confirmed liveness.
Warnings
- —No documentation available — /docs, /pricing, /api, and /README pages all render only 'Connect wallet'
- —No OpenAPI or schema definition found for any endpoint
- —The purpose of '/api/v1/invoices/45' ('Premium API Access') is unclear — it does not match any of the documented endpoint categories on the landing page
- —No request or response examples available; input parameters are unknown
Citations
- —All endpoints priced at $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —Endpoint categories include Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructurehttps://lowpaymentfee.com
- —x402 challenge returns maxAmountRequired of 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base, equaling $0.02https://lowpaymentfee.com/api/v1/invoices/45
- —Documentation pages (/docs, /pricing, /api, /README) render only 'Connect wallet' with no contenthttps://lowpaymentfee.com/docs