Pay-per-request API platform on Base via x402 — $0.02/call for data, AI, finance, and utility endpoints.
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, settled in USDC on the Base network.
The specific endpoint at `/api/v1/carts/33` is listed as "Premium API Access" and returns a 402 challenge requesting up to 20,000 base units of USDC (0.02 USD, since USDC uses 6 decimals) on Base. Payment is made via the x402 protocol's `exact` scheme with no API keys or rate limits required. The payment address is `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3`, and the endpoint accepts POST requests returning `application/json`.
Documentation beyond the landing page is extremely sparse — the /docs, /api, /pricing, and /README pages all render only a "Connect wallet" prompt with no additional technical content. There is no OpenAPI spec, no request/response schema documentation, and no examples of what the `/api/v1/carts/33` endpoint actually returns. The platform advertises no API keys, no rate limits, and instant access, but the actual functionality behind this specific cart endpoint is unclear from available materials.
Capabilities
Use cases
- —Programmatic access to paid API endpoints without traditional API key management
- —Agent-driven workflows that need on-demand API calls settled in crypto
- —Testing x402 payment protocol integrations with low-cost endpoints
Fit
Best for
- —Developers experimenting with x402 pay-per-request patterns
- —AI agents that need keyless, instant API access on Base
- —Low-volume consumers who want no subscription commitments
Not for
- —Users needing detailed API documentation or guaranteed SLAs
- —High-volume production workloads where per-request crypto settlement adds overhead
- —Anyone without a Base-compatible USDC wallet
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/carts/33 \
-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 pricing and payment details. However, there is no OpenAPI spec, no request/response schema, no documentation beyond a landing page, and the specific purpose of /api/v1/carts/33 is undocumented. The docs, pricing, and README pages are all blank beyond a wallet connect prompt.
Warnings
- —No OpenAPI or schema documentation available for any endpoint
- —The /docs, /pricing, /api, and /README pages contain no usable content — only a 'Connect wallet' prompt
- —The specific purpose and response format of /api/v1/carts/33 ('Premium API Access') is not documented anywhere
- —The broader platform lists many endpoints but none have documented request/response schemas
- —Cannot verify that the advertised AI, finance, and data endpoints actually function as described
Citations
- —All endpoints priced at $0.02 per request with no API keys, no rate limits, on Base networkhttps://lowpaymentfee.com
- —Platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com
- —x402 challenge returns maxAmountRequired of 20000 base units of USDC (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Basehttps://lowpaymentfee.com/api/v1/carts/33