Pay-per-request API platform on Base (USDC) via x402 — $0.02/call, no API keys needed.
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/54` 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/54`) is labeled "Premium API Access" but its specific functionality is not documented beyond that label. The docs, pricing, and README pages all returned only a "Connect wallet" prompt with no additional content. Without further documentation or an OpenAPI schema, the exact request/response format for this endpoint is unknown.
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
- —Programmatic purchasing via x402 protocol without subscription commitments
Fit
Best for
- —Developers wanting zero-commitment, per-call API pricing
- —AI agents that can settle x402 payments autonomously
- —Users already holding USDC on Base who want frictionless API access
Not for
- —Users who need detailed API documentation or OpenAPI specs before integrating
- —High-volume callers who would benefit from bulk/subscription pricing
- —Developers who cannot settle USDC payments on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/carts/54 \
-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 OpenAPI schema, no documentation beyond a label, no request/response examples, and the docs/pricing/README pages are all empty stubs showing only 'Connect wallet'. The actual functionality of /api/v1/carts/54 is entirely opaque.
Warnings
- —No OpenAPI or schema documentation available for this endpoint
- —The endpoint name 'Premium API Access' and path '/api/v1/carts/54' give no indication of what data or service is returned
- —All documentation pages (docs, pricing, README, api) returned only 'Connect wallet' with no usable content
- —Request and response formats are completely unknown — integration requires trial and error
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/54
- —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/54
- —The platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com