Pay-per-call API platform on Base (USDC) covering data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-enabled API platform that offers a broad catalog of pay-per-request endpoints settled in USDC on the Base network. The specific endpoint at `/api/v1/invoices/31` is listed as "Premium API Access" and charges up to $0.02 per call (20,000 base units of USDC with 6 decimals). The platform advertises no API keys, no rate limits, and instant access — callers simply attach an x402 payment header to each request.
The site organizes its endpoints into 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 listed endpoints share the same $0.02 per-request pricing.
Documentation is extremely sparse — the docs, API, pricing, and README pages all render only a "Connect wallet" prompt with no further technical detail. There is no OpenAPI schema, no request/response examples, and no description of what the `/api/v1/invoices/31` endpoint specifically returns. The x402 challenge confirms the endpoint is live and accepts POST requests, but the actual payload format and response structure are unknown.
Capabilities
Use cases
- —Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API key management
- —Fetching real-time finance data like token quotes, exchange rates, and gas estimates on a per-call basis
- —Running utility operations such as geocoding, validation, and data conversion with micropayments
- —Integrating pay-per-use data analytics and reporting into agent workflows
Fit
Best for
- —Agents or developers who want keyless, pay-per-request API access
- —Low-volume or bursty workloads where subscription pricing is wasteful
- —Crypto-native applications already operating on Base with USDC
Not for
- —Users needing detailed API documentation or guaranteed SLAs before integrating
- —High-volume production workloads where $0.02/request adds up significantly
- —Developers who cannot transact in USDC on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/31 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The x402 challenge confirms the endpoint is live and pricing is clear ($0.02 USDC on Base), but there is zero documentation on request/response schemas, no OpenAPI spec, and the docs pages are empty. The specific purpose of /api/v1/invoices/31 is unclear beyond the generic label 'Premium API Access'.
Warnings
- —No OpenAPI schema or request/response documentation available
- —Docs, API, pricing, and README pages all render only 'Connect wallet' with no content
- —The specific function of /api/v1/invoices/31 is undocumented — it is unclear what data or service it provides
- —No examples of expected input or output formats
Citations
- —The endpoint returns a 402 challenge with maxAmountRequired of 20000 in USDC (asset 0x8335…) on Base networkhttps://lowpaymentfee.com/api/v1/invoices/31
- —All listed endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —The platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com