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/23` is listed as "Premium API Access" and requires a maximum payment of 20,000 base units of USDC (i.e., $0.02) per call. The platform uses the x402 protocol, meaning no API keys or accounts are needed — callers simply attach an X-PAYMENT header with a valid payment proof.
The broader platform advertises 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 listed at the same $0.02 per request price point.
Documentation is extremely sparse — the docs, API, pricing, and README pages all render only a "Connect wallet" prompt with no further content. There is no OpenAPI schema, no request/response examples, and no detailed documentation for any endpoint. The invoices endpoint's purpose is unclear from the available material; the name "Premium API Access" is generic and does not describe what data or functionality is returned. The endpoint is confirmed live via a valid 402 challenge.
Capabilities
Use cases
- —Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API key registration
- —Fetching real-time finance data like token quotes, gas estimates, and exchange rates on a per-call basis
- —Running data analytics queries and exporting data with instant crypto-settled micropayments
- —Using utility services like geocoding and validation without subscription commitments
Fit
Best for
- —Developers wanting instant API access without signup or API key management
- —Agents and bots that can settle payments programmatically via x402 on Base
- —Low-volume or sporadic API consumers who prefer pay-per-use over subscriptions
Not for
- —Users who need detailed API documentation or OpenAPI specs before integrating
- —High-volume consumers who would benefit from bulk pricing or rate-limited plans
- —Developers without access to USDC on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/23 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>"Endpoint
Quality
The endpoint is confirmed live via a valid x402 402 challenge, but documentation is essentially nonexistent — all doc pages show only 'Connect wallet'. There is no OpenAPI schema, no request/response examples, and the specific purpose of the /api/v1/invoices/23 endpoint is unclear. The listing is effectively a stub with pricing info.
Warnings
- —Documentation pages (docs, API, pricing, README) all render only 'Connect wallet' with no usable content
- —No OpenAPI schema or request/response examples available for any endpoint
- —The purpose of /api/v1/invoices/23 ('Premium API Access') is not explained — unclear what data it returns
- —The broader platform lists many endpoints but none have documented input/output schemas
Citations
- —The endpoint returns a valid x402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/invoices/23
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/invoices/23
- —All endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —Platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com
- —Documentation, API, pricing, and README pages render only 'Connect wallet'https://lowpaymentfee.com/docs