Pay-per-call API platform on Base with USDC payments via x402 — $0.02/request, no API keys required.
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/24` is listed as "Premium API Access" and returns a 402 challenge requesting up to 20,000 base units of USDC (i.e., $0.02) 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 uniformly priced at $0.02 per request.
Note that while the landing page lists many endpoints, the crawled documentation pages (`/docs`, `/api`, `/pricing`, `/README`) all returned only a "Connect wallet" prompt with no substantive content. There is no OpenAPI schema, no request/response examples, and no detailed documentation available. The actual functionality behind this specific invoices endpoint and the other listed endpoints cannot be verified from the crawl material alone.
Capabilities
Use cases
- —Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without subscription commitments
- —Fetching real-time financial data like token quotes, exchange rates, and gas estimates on a per-call basis
- —Running utility operations like geocoding, validation, and data conversion with micropayments
- —Programmatic agents purchasing API calls autonomously via x402 USDC payments
Fit
Best for
- —Developers wanting zero-commitment, pay-as-you-go API access
- —AI agents that need to autonomously purchase API calls with crypto
- —Projects on Base network already holding USDC
Not for
- —Users needing high-volume bulk pricing or enterprise SLAs
- —Developers who require detailed API documentation and typed schemas before integration
- —Users without USDC on Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/24 \
-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 accepts USDC on Base at $0.02/call. However, there is no OpenAPI schema, no request/response examples, and all documentation pages returned only 'Connect wallet' with no content. The actual functionality of the invoices/24 endpoint is undocumented and unclear.
Warnings
- —No OpenAPI or schema documentation available — all doc pages (/docs, /api, /pricing, /README) return only 'Connect wallet'
- —The specific purpose of /api/v1/invoices/24 ('Premium API Access') is not explained anywhere in the crawled material
- —No request body schema or response format documented for any endpoint
- —Cannot verify that the listed AI, finance, and utility endpoints actually function as described
Citations
- —The endpoint returns a 402 challenge requesting up to 20,000 base units of USDC ($0.02) on Base networkhttps://lowpaymentfee.com/api/v1/invoices/24
- —The platform lists endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories, all at $0.02/requesthttps://lowpaymentfee.com
- —Platform advertises no API keys, no rate limits, instant access, and Base network settlementhttps://lowpaymentfee.com
- —USDC asset address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base with payment to 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3https://lowpaymentfee.com/api/v1/invoices/24