Pay-per-call API platform on Base network via x402 — $0.02/request in USDC.
What it does
lowpaymentfee.com is a pay-per-request API platform that uses the x402 protocol to accept USDC payments on the Base network. The specific endpoint `/api/v1/invoices/2` is labeled "Premium API Access" and requires a payment of up to 20,000 base units of USDC (0.02 USD) per call. The platform advertises no API keys, no rate limits, and instant access — you simply attach an x402 payment header to each request.
The broader platform offers 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/request price point.
This particular endpoint (`/api/v1/invoices/2`) is live and returns a proper 402 challenge. However, the documentation pages (docs, pricing, README) all returned only a "Connect wallet" prompt with no substantive content, so the actual request/response schemas for this endpoint and others are unknown. There is no OpenAPI spec or detailed documentation available from the crawl.
Capabilities
Use cases
- —Accessing premium API data with per-request USDC micropayments on Base
- —Programmatic invoice retrieval without subscription or API key management
- —Agent-driven API consumption where each call is individually settled on-chain
Fit
Best for
- —Developers wanting zero-commitment pay-as-you-go API access
- —AI agents that can settle x402 payments autonomously
- —Users who prefer crypto micropayments over traditional API subscriptions
Not for
- —Users needing detailed API documentation or OpenAPI specs before integrating
- —High-volume consumers who would benefit from bulk pricing or subscriptions
- —Developers who cannot transact in USDC on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/2 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is live and returns a valid x402 402 challenge, confirming it works. However, there is no OpenAPI spec, no documentation beyond a landing page listing, no request/response schema, and all doc pages return only 'Connect wallet'. The actual functionality behind '/api/v1/invoices/2' is opaque.
Warnings
- —No OpenAPI specification or detailed documentation available
- —All documentation pages (docs, pricing, README) returned only 'Connect wallet' with no content
- —The actual request body schema and response format for /api/v1/invoices/2 are completely unknown
- —The endpoint name 'Premium API Access' is generic and does not describe what data or service is returned
Citations
- —The endpoint returns a 402 challenge with maxAmountRequired of 20000 base units of USDC on Base networkhttps://lowpaymentfee.com/api/v1/invoices/2
- —All 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
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/invoices/2