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 catalog of pay-per-request 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.
The specific endpoint being listed here — `/api/v1/invoices/42` — is described as "Premium API Access" and returns a live x402 challenge requesting up to 20,000 base units of USDC (i.e., $0.02) on Base. The payment scheme is "exact," meaning a single per-call payment is required. The endpoint accepts HTTP POST and returns application/json. No API keys or rate limits are advertised; access is gated entirely by the x402 payment protocol.
Documentation is extremely sparse. The docs, API, pricing, and README pages all render only a "Connect wallet" prompt with no substantive content. There is no OpenAPI schema, no request/response examples, and no detailed description of what the `/api/v1/invoices/42` endpoint actually returns. The broader site catalog suggests a variety of services, but the specific behavior of this invoice endpoint is unclear from available materials.
Capabilities
Use cases
- —Accessing premium API data without signing up for an account or managing API keys
- —Making one-off paid API calls from autonomous agents using x402 on Base
- —Retrieving invoice or financial data via a single micropayment
Fit
Best for
- —Agents or developers who want keyless, pay-as-you-go API access
- —Use cases requiring low-friction micropayments ($0.02/call) on Base
- —Scenarios where no subscription or rate-limit management is desired
Not for
- —Users who need detailed API documentation or guaranteed SLAs before integrating
- —High-volume use cases where per-call pricing may be less economical than bulk plans
- —Anyone without access to USDC on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/42 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is live and returns a valid x402 challenge, confirming it is operational. However, documentation is essentially nonexistent — all doc pages show only 'Connect wallet.' There is no OpenAPI schema, no request/response examples, and the purpose of the specific /api/v1/invoices/42 endpoint is not explained beyond the generic label 'Premium API Access.' The listing is largely a stub.
Warnings
- —Documentation pages (/docs, /api, /pricing, /README) all render only 'Connect wallet' with no substantive content.
- —No OpenAPI or schema available; request and response formats for this endpoint are unknown.
- —The specific purpose and output of /api/v1/invoices/42 is unclear — 'Premium API Access' is generic.
- —The broader site lists many endpoints but none have documented schemas or example payloads.
Citations
- —The endpoint returns a live x402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/invoices/42
- —All endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant access on the Base networkhttps://lowpaymentfee.com
- —The site offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com
- —USDC asset address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base networkhttps://lowpaymentfee.com/api/v1/invoices/42