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 at `/api/v1/invoices/38` is listed as "Premium API Access" and returns a standard x402 challenge requiring payment of up to 20,000 base units of USDC (i.e., $0.02) per call. No API keys or rate limits are advertised — access is gated purely by the x402 payment protocol.
The platform organizes its APIs 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/request pricing. The invoices endpoint probed here does not clearly map to any of those named categories, so its exact functionality is uncertain.
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 spec, no request/response examples, and no detailed description of what any endpoint actually returns. The endpoint is confirmed live (402 challenge captured), but the lack of documentation makes it difficult to know what payload to send or what response to expect.
Capabilities
Use cases
- —Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API key management
- —Fetching real-time financial data such as token quotes, gas estimates, and exchange rates
- —Running utility operations like geocoding, validation, and data conversion on a per-request basis
Fit
Best for
- —Developers wanting zero-commitment, pay-as-you-go API access
- —AI agents that can settle x402 payments autonomously on Base
- —Projects needing low-cost micropayment-gated API calls without subscription overhead
Not for
- —Users who need detailed API documentation or guaranteed SLAs before integrating
- —High-volume production workloads requiring bulk pricing or dedicated support
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/38 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is confirmed live with a valid x402 challenge and clear pricing ($0.02 USDC on Base). However, documentation is essentially nonexistent — all doc pages show only 'Connect wallet'. There is no OpenAPI spec, no request/response examples, and the specific purpose of the /invoices/38 endpoint is unclear. This is effectively a stub listing.
Warnings
- —Documentation pages (/docs, /api, /pricing, /README) all render only 'Connect wallet' with no usable content
- —No OpenAPI or schema available — request format and response structure are unknown
- —The specific endpoint /api/v1/invoices/38 ('Premium API Access') does not map to any of the named API categories on the homepage; its actual functionality is unclear
- —No examples of successful responses are available anywhere in the crawl
Citations
- —The endpoint returns a 402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/invoices/38
- —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 APIs in four categories: Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructurehttps://lowpaymentfee.com
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/invoices/38