x402-gated premium API endpoint on Base, pay-per-call with USDC.
What it does
This endpoint at `/api/v1/cards/54` is part of the lowpaymentfee.com platform, a collection of x402-protocol pay-per-request APIs spanning data analytics, AI/ML inference, finance/Web3 data, and infrastructure utilities. The specific `/api/v1/cards/54` resource is labeled "Premium API Access" but its exact functionality is not documented beyond that label — it is not listed among the publicly advertised endpoints on the site's landing page, which focus on analytics, AI, finance, and utility services.
Payment is handled via the x402 protocol on the Base network using USDC (contract `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`). The maximum amount required per call is 20,000 base units of USDC, which equals $0.02 (two cents) given USDC's 6 decimal places. The platform advertises a flat $0.02/request pricing model with no API keys, no rate limits, and instant access. The endpoint accepts HTTP POST requests and returns `application/json`.
Documentation is extremely sparse. The `/docs`, `/api`, `/pricing`, and `/README` pages all render only a "Connect wallet" prompt with no additional content. There is no OpenAPI schema, no request/response examples, and no description of what data or service `/api/v1/cards/54` actually returns. The endpoint is confirmed live (returns a proper 402 x402 challenge), but without documentation the actual payload and use case remain unknown.
Capabilities
Use cases
- —Accessing a premium data or service endpoint via x402 micropayment on Base
- —Programmatic pay-per-call API consumption without API keys or subscriptions
- —Agent-driven API access using USDC on Base L2
Fit
Best for
- —Developers or agents wanting keyless, pay-per-request API access
- —x402-compatible clients on the Base network
- —Low-cost micropayment API experimentation
Not for
- —Users needing detailed documentation or guaranteed SLAs before integrating
- —Use cases requiring known, well-documented response schemas
- —High-volume batch processing where per-request pricing may not be optimal
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/cards/54 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is confirmed live with a valid x402 challenge and clear pricing ($0.02/request in USDC on Base). However, there is no documentation, no OpenAPI schema, no request/response examples, and the specific purpose of `/api/v1/cards/54` is entirely undocumented — it doesn't appear in the site's own listed endpoints. This is effectively a stub listing.
Warnings
- —The specific endpoint /api/v1/cards/54 is not listed among the publicly advertised APIs on the landing page; its purpose is unknown.
- —No documentation exists — /docs, /pricing, /api, and /README pages all show only a 'Connect wallet' prompt.
- —No OpenAPI schema, request format, or response examples are available.
- —The 'Premium API Access' label provides no indication of what data or service is returned.
Citations
- —The platform advertises $0.02/request pricing with no API keys, no rate limits, and instant access on the Base network.https://lowpaymentfee.com
- —The x402 challenge specifies maxAmountRequired of 20000 base units of USDC (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base, equaling $0.02.https://lowpaymentfee.com/api/v1/cards/54
- —The /docs, /api, /pricing, and /README pages render only a 'Connect wallet' prompt with no additional documentation.https://lowpaymentfee.com/docs