x402-gated premium API endpoint on Base, pay $0.02 per request in USDC.
What it does
lowpaymentfee.com hosts a collection of x402-protocol pay-per-request API endpoints on the Base network, settling in USDC. The specific endpoint `/api/v1/cards/5` is listed as "Premium API Access" and costs $0.02 per call (20,000 base units of USDC with 6 decimals). Payment is handled via the x402 exact-payment scheme — no API keys, no rate limits, and no sign-up required. You send a POST request with an `X-PAYMENT` header containing a valid payment proof, and the endpoint returns JSON.
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.
The specific functionality of `/api/v1/cards/5` is not documented beyond the label "Premium API Access." There is no OpenAPI schema, no request/response examples, and the docs, pricing, and README pages all render only a "Connect wallet" prompt with no additional content. The endpoint is confirmed live (returns a proper 402 challenge), but what data or service it actually provides is unclear.
Capabilities
Use cases
- —Programmatic access to a premium API resource with per-call USDC micropayments
- —Agent-driven workflows that need keyless, on-demand API access settled on Base
- —Demonstrating or testing x402 payment protocol integrations
Fit
Best for
- —Developers experimenting with x402 pay-per-call protocols
- —AI agents that can autonomously pay for API calls via USDC on Base
- —Users who want no-signup, no-rate-limit API access
Not for
- —Users who need detailed documentation or guaranteed SLAs before integrating
- —Anyone requiring non-crypto payment methods
- —Use cases needing high-volume batch access at lower per-unit cost
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/cards/5 \
-H "X-PAYMENT: <valid-x402-payment-proof>" \
-H "Content-Type: application/json"Endpoint
Quality
The endpoint is confirmed live with a valid 402 challenge and clear pricing ($0.02 USDC on Base). However, there is no documentation of what the endpoint actually returns, no OpenAPI schema, no request/response examples, and the docs pages are empty. The purpose of '/api/v1/cards/5' is entirely opaque beyond the generic label 'Premium API Access.'
Warnings
- —No documentation available — docs, pricing, and README pages all render only 'Connect wallet' with no content.
- —The specific functionality of /api/v1/cards/5 is unknown; 'Premium API Access' is not descriptive.
- —No OpenAPI schema or request/response examples are provided.
- —No information about what 'cards/5' refers to — could be anything.
Citations
- —The endpoint returns a 402 challenge with maxAmountRequired of 20000 base units of USDC on Base networkhttps://lowpaymentfee.com/api/v1/cards/5
- —All endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —The platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com
- —USDC asset address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/cards/5