Pay-per-request API platform on Base network via x402 — $0.02/call in USDC.
What it does
lowpaymentfee.com is an x402-enabled API platform that offers a broad catalog of endpoints spanning data analytics, AI/ML inference, finance/Web3 data, and utility services. All endpoints are paid per-request using USDC on the Base network, with no API keys, no rate limits, and no commitments required. The specific endpoint at `/api/v1/carts/3` is listed as "Premium API Access" and returns an x402 challenge requesting up to 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02 per call (USDC uses 6 decimals).
The platform advertises categories including 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 listed endpoints share the same $0.02 price point. The x402 challenge uses the "exact" payment scheme, pays to address 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3, and allows a maximum timeout of 300 seconds.
Documentation is extremely sparse — the /docs, /api, /pricing, 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 examples of what the `/api/v1/carts/3` endpoint actually returns. The purpose of the "carts/3" resource specifically is unclear from the available material.
Capabilities
Use cases
- —Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API key management
- —Fetching real-time finance data like token quotes, gas estimates, and exchange rates on a per-call basis
- —Running data analytics queries and exporting data with per-request USDC micropayments
- —Using utility services like geocoding and validation without subscription commitments
Fit
Best for
- —Developers wanting zero-friction API access without signup or API keys
- —Agents and bots that can settle payments in USDC on Base via x402
- —Low-volume or bursty workloads where per-request pricing is more economical than subscriptions
Not for
- —High-volume production workloads where subscription pricing would be cheaper
- —Users who cannot transact in USDC on the Base network
- —Applications requiring detailed SLAs, rate-limit guarantees, or enterprise support
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/carts/3 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The x402 challenge is live and well-formed, confirming the endpoint works and pricing is clear ($0.02 USDC on Base). However, documentation is effectively absent — all doc pages show only 'Connect wallet'. There is no OpenAPI spec, no request/response schema, no examples, and the specific purpose of '/api/v1/carts/3' is unexplained. The broad catalog of endpoints is listed on the homepage but none have documented schemas.
Warnings
- —No documentation available — /docs, /pricing, /api, and /README all render only 'Connect wallet'
- —No OpenAPI or schema specification found for any endpoint
- —The specific purpose and expected input/output of /api/v1/carts/3 ('Premium API Access') is undocumented
- —Cannot verify that the advertised AI, finance, and utility endpoints actually function as described
Citations
- —All endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —The x402 challenge for /api/v1/carts/3 requests maxAmountRequired of 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Basehttps://lowpaymentfee.com/api/v1/carts/3
- —Available API categories include Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructurehttps://lowpaymentfee.com
- —Documentation pages (/docs, /api, /pricing, /README) show only 'Connect wallet' with no further contenthttps://lowpaymentfee.com/docs