x402-gated premium API endpoint on Base, payable in USDC per request.
What it does
This endpoint at `/api/v1/carts/14` is part of the lowpaymentfee.com platform, which offers a collection of x402-protocol pay-per-request APIs spanning data & analytics, AI/ML inference, finance & Web3, and infrastructure utilities. The specific `/carts/14` endpoint is labeled "Premium API Access" but its exact functionality is not documented beyond that label. The platform advertises a flat $0.02 per request pricing model across its other endpoints, though this particular endpoint's x402 challenge specifies a `maxAmountRequired` of 20000 (in USDC base units on Base network, which equals $0.02 given USDC's 6 decimals).
Payment is handled via the x402 protocol using the "exact" scheme on the Base L2 network. The accepted asset is USDC (contract `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`). No API keys or rate limits are required — callers simply attach an `X-PAYMENT` header with a valid payment proof. The endpoint accepts POST requests and returns `application/json`. The payment timeout is 300 seconds.
The broader lowpaymentfee.com platform lists 16 endpoints across four categories but provides minimal documentation — the docs, API, pricing, and README pages all render only a "Connect wallet" prompt with no substantive content. Because the specific purpose of `/api/v1/carts/14` is unclear (it does not appear in the site's listed API catalog), its actual functionality cannot be confirmed from available sources.
Capabilities
Use cases
- —Programmatic access to a premium API resource with per-request USDC micropayments
- —Agent-driven workflows that need keyless, on-demand API access on Base
- —Demonstrating x402 protocol payment flows in development or testing
Fit
Best for
- —Developers experimenting with x402 pay-per-request protocols
- —Agents that can sign USDC payments on Base L2
- —Use cases requiring no-signup, no-API-key access
Not for
- —Users who need detailed API documentation before integrating
- —High-volume use cases where per-request payment overhead is impractical
- —Anyone without a Base-network USDC wallet
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/carts/14 \
-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 the actual functionality of /api/v1/carts/14 is undocumented — it doesn't appear in the site's own API catalog. Documentation pages are empty (just 'Connect wallet'). No request/response schema, no examples, and no OpenAPI spec are available.
Warnings
- —The endpoint /api/v1/carts/14 is not listed among the platform's advertised APIs — its specific functionality is unknown.
- —All documentation pages (docs, API, pricing, README) return only a 'Connect wallet' prompt with no actual content.
- —No request body schema or response schema is documented; callers cannot know what to send or expect back.
- —The 'Premium API Access' label is generic and does not describe what the endpoint does.
Citations
- —The x402 challenge returns maxAmountRequired of 20000 USDC base units on Base network with the exact schemehttps://lowpaymentfee.com/api/v1/carts/14
- —The platform advertises $0.02 per request pricing with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —The USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/carts/14
- —Documentation, API, pricing, and README pages render only a 'Connect wallet' prompthttps://lowpaymentfee.com/docs