Pay-per-call API platform on Base via x402 — 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 set of 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 with no API keys, rate limits, or commitments required.
The specific endpoint at `/api/v1/invoices/6` is listed as "Premium API Access" and returns a standard x402 challenge requesting up to 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02 given USDC's 6 decimals. Payment is made via the x402 exact scheme with a 300-second timeout. The endpoint accepts HTTP POST and returns application/json.
Documentation beyond the landing page is extremely sparse — the /docs, /pricing, /api, and /README pages all render only a "Connect wallet" prompt with no additional technical content. There is no OpenAPI spec, no request/response schema documentation, and no example payloads available. The actual functionality behind the `/api/v1/invoices/6` path is unclear; it may be an invoice retrieval or generation endpoint, but this is not documented. The platform appears live and functional based on the 402 challenge response.
Capabilities
Use cases
- —Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API key signup
- —Fetching real-time financial data like token quotes, gas estimates, and exchange rates on a per-call basis
- —Running data analytics queries and exporting reports with pay-as-you-go pricing
- —Using utility services like geocoding and validation without subscription commitments
Fit
Best for
- —Developers who want instant API access without registration or API keys
- —Agents and bots that can settle payments in USDC on Base via x402
- —Low-volume or sporadic API consumers who prefer per-request pricing over subscriptions
Not for
- —High-volume production workloads where $0.02/request adds up significantly
- —Users who need detailed API documentation, SDKs, or guaranteed SLAs
- —Developers without access to USDC on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/6 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is live and returns a valid x402 challenge, and the landing page lists available endpoints with pricing. However, there is no OpenAPI spec, no request/response schemas, no documentation beyond the homepage, and the specific purpose of /api/v1/invoices/6 is undocumented. This is effectively a stub listing.
Warnings
- —No OpenAPI specification or schema documentation available
- —All documentation pages (/docs, /pricing, /api, /README) render only 'Connect wallet' with no content
- —The specific purpose and expected request/response format of /api/v1/invoices/6 is undocumented
- —The breadth of advertised endpoints (16+ across 4 categories) cannot be verified from available material
Citations
- —All endpoints are priced at $0.02 per request with no API keys, rate limits, or commitmentshttps://lowpaymentfee.com
- —Platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com
- —Payment is in USDC on Base networkhttps://lowpaymentfee.com
- —x402 challenge returns maxAmountRequired of 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Basehttps://lowpaymentfee.com/api/v1/invoices/6