Pay-per-request API platform on Base (USDC) via x402 — $0.02/call, no API keys required.
What it does
lowpaymentfee.com is a pay-per-request API platform that uses the x402 protocol to accept USDC payments on the Base network. The specific endpoint `/api/v1/carts/44` 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 platform advertises no API keys, no rate limits, and instant access — callers simply attach an X-PAYMENT header with a valid x402 payment proof.
The broader platform offers 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.
This particular endpoint (`/api/v1/carts/44`) is labeled "Premium API Access" but its actual functionality is unclear — the description is generic and no request/response schema is documented beyond the x402 challenge's indication that it accepts HTTP POST and returns `application/json`. The docs, pricing, and API pages on the site all render only a "Connect wallet" prompt with no additional technical documentation.
Capabilities
Use cases
- —Accessing premium API data with per-request USDC micropayments on Base
- —Agent-driven workflows that need keyless, pay-as-you-go API access
- —Testing x402 protocol integrations with a low-cost endpoint
Fit
Best for
- —Developers experimenting with x402 payment protocol
- —AI agents that need frictionless, keyless API access
- —Users who want to avoid subscriptions and pay only per call
Not for
- —Users who need detailed API documentation or OpenAPI specs before integrating
- —High-volume consumers who would benefit from bulk pricing or subscriptions
- —Anyone without a Base-network USDC wallet
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/carts/44 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>"Endpoint
Quality
The endpoint is live (402 challenge confirmed) and pricing is clear ($0.02 USDC on Base), but there is no documentation, no OpenAPI schema, no request/response examples, and the actual functionality behind '/api/v1/carts/44' is completely opaque. The docs pages render only 'Connect wallet' with no technical content.
Warnings
- —No documentation available — docs, pricing, API, and README pages all show only 'Connect wallet'
- —The actual functionality of /api/v1/carts/44 ('Premium API Access') is undocumented and unclear
- —No request body schema or response schema is provided beyond the x402 outputSchema stub
- —No OpenAPI or machine-readable API specification found
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/carts/44
- —The platform advertises $0.02/request pricing with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —The USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/carts/44
- —Docs, pricing, API, and README pages render only 'Connect wallet' with no technical contenthttps://lowpaymentfee.com/docs