Pay-per-request API suite on Base via x402 — data, AI, finance, and utility endpoints at $0.02/call.
What it does
lowpaymentfee.com offers a collection of pay-per-request API endpoints settled via the x402 protocol on the Base network using USDC. The specific endpoint at `/api/v1/invoices/12` 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 broader platform advertises four categories of APIs: 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 uniformly at $0.02 per request with no API keys, no rate limits, and no minimum commitments.
Documentation is extremely sparse — the docs, API, pricing, and README pages all render only a "Connect wallet" prompt with no further technical detail. There is no OpenAPI schema, no request/response examples, and no description of what the `/api/v1/invoices/12` endpoint actually returns. The endpoint is live and responds with a valid x402 challenge, but without documentation it is unclear what payload to send or what data to expect back.
Capabilities
Use cases
- —Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API key management
- —Fetching financial data like token quotes, exchange rates, and gas estimates on a per-call basis
- —Running data analytics queries and exporting data with micropayments
- —Using utility services like geocoding, validation, and conversion via crypto-settled requests
Fit
Best for
- —Developers wanting zero-commitment, pay-as-you-go API access
- —Agents and bots that can settle payments via x402 on Base
- —Projects needing low-friction access to diverse API categories without signup
Not for
- —Production workloads requiring detailed API documentation and SLAs
- —Users who cannot transact in USDC on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/12 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is live and returns 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 no explanation of what the invoices/12 endpoint actually does. The listing is effectively a stub.
Warnings
- —Documentation pages (docs, API, pricing, README) all render only 'Connect wallet' with no usable content
- —No OpenAPI or schema available — request and response formats are unknown
- —The specific endpoint /api/v1/invoices/12 is labeled 'Premium API Access' but its actual functionality is undocumented
- —Cannot verify what data or service any of the advertised endpoints actually provide
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/12
- —The platform advertises APIs across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories, all at $0.02/requesthttps://lowpaymentfee.com
- —Pricing is $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —USDC asset address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/invoices/12