x402-gated API platform on Base offering data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-enabled API marketplace that exposes a variety 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 pay-per-call at $0.02 per request, settled in USDC on the Base network.
The specific endpoint at `/api/v1/carts/90` is listed as "Premium API Access" and returns a live x402 challenge requesting up to 20,000 units of USDC (0x8335…2913 on Base) via the "exact" payment scheme. The payment is directed to address 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3 with a 300-second timeout. The endpoint accepts HTTP POST and returns application/json.
Documentation is extremely sparse — the /docs, /pricing, /api, and /README pages all render only a "Connect wallet" prompt with no further content. There is no OpenAPI spec, no request/response schema documentation, and no usage examples available. The exact purpose of the `/api/v1/carts/90` endpoint (as opposed to the other listed endpoints) is unclear from the available material. The maxAmountRequired of 20,000 USDC units likely corresponds to $0.02 (assuming 6-decimal USDC), consistent with the site's advertised pricing.
Capabilities
Use cases
- —Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API keys
- —Fetching real-time financial data and crypto quotes on a per-request basis
- —Running geocoding or data validation utilities with micropayments
- —Exporting analytics data or generating reports via pay-as-you-go calls
Fit
Best for
- —Agents or developers wanting keyless, pay-per-call API access
- —Crypto-native applications that can settle payments in USDC on Base
- —Low-volume or sporadic API usage where subscriptions are wasteful
Not for
- —High-volume production workloads needing guaranteed SLAs and detailed documentation
- —Users without a Base-compatible wallet or USDC holdings
- —Applications requiring well-documented request/response schemas before integration
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/carts/90 \
-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 APIs with pricing. However, there is no OpenAPI spec, no request/response schema, no documentation beyond a wallet-connect prompt, and the specific purpose of /api/v1/carts/90 is undocumented. This is effectively a stub listing.
Warnings
- —No OpenAPI or schema documentation available for any endpoint
- —All documentation pages (/docs, /pricing, /api, /README) render only 'Connect wallet' with no content
- —The specific endpoint /api/v1/carts/90 ('Premium API Access') is not listed among the site's advertised APIs — its purpose is unclear
- —No request body schema or response schema is documented anywhere
- —Cannot verify what data or functionality this endpoint actually provides
Citations
- —The site advertises $0.02 per request pricing with no API keys, no rate limits, and instant access on the Base networkhttps://lowpaymentfee.com
- —Available API categories include Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructurehttps://lowpaymentfee.com
- —The x402 challenge requests maxAmountRequired of 20000 units of USDC (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base with a 300-second timeouthttps://lowpaymentfee.com/api/v1/carts/90
- —Documentation pages /docs, /pricing, /api, and /README all show only 'Connect wallet'https://lowpaymentfee.com/docs