x402-gated API platform on Base offering data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-protocol API marketplace that gates access to a variety of endpoints behind per-request USDC micropayments on the Base network. The specific endpoint at `/api/v1/carts/83` is listed as "Premium API Access" and accepts POST requests with payment via the x402 exact scheme. The maximum amount required is 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02 per call.
The broader platform advertises four categories of APIs: 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 listed at the same $0.02/request price point. The platform claims no API keys, no rate limits, and instant access — payment is the only authentication mechanism.
Documentation beyond the landing page is extremely sparse; the /docs, /api, /pricing, and /README pages all render only a "Connect wallet" prompt with no additional technical content. There is no OpenAPI spec, no request/response schema documentation, and no usage examples available from the crawl. The specific functionality behind the `/api/v1/carts/83` endpoint is unclear — the name "Premium API Access" and the carts path suggest it may be a shopping-cart or e-commerce related resource, but this is not documented.
Capabilities
Use cases
- —Programmatic access to paid API endpoints without traditional API key management
- —Agent-driven workflows that need to pay per call using on-chain USDC
- —Testing x402 payment protocol integrations against a live endpoint
Fit
Best for
- —Developers experimenting with x402 payment-gated APIs
- —AI agents that can settle USDC payments on Base for per-call access
- —Projects needing low-cost ($0.02) pay-as-you-go API access without subscriptions
Not for
- —Users who need detailed API documentation or OpenAPI specs before integrating
- —High-throughput use cases where per-request on-chain payment overhead is impractical
- —Anyone without a Base-compatible USDC wallet
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/carts/83 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is live and returns a valid x402 402 challenge with clear pricing. However, documentation is essentially nonexistent — all doc pages show only 'Connect wallet'. There is no OpenAPI spec, no request/response schema, no examples, and the purpose of the specific /carts/83 endpoint is unclear. The listing is effectively a stub with confirmed liveness.
Warnings
- —No documentation available beyond landing page — /docs, /api, /pricing, /README all show only 'Connect wallet'
- —No OpenAPI or schema definition found for any endpoint
- —The specific purpose and expected input/output of /api/v1/carts/83 is undocumented
- —No request or response examples available
- —The breadth of advertised API categories (AI, finance, data, infrastructure) cannot be verified from available material
Citations
- —The endpoint returns a 402 x402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/carts/83
- —USDC asset address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base networkhttps://lowpaymentfee.com/api/v1/carts/83
- —Platform advertises $0.02/request pricing with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —Four API categories listed: Data & Analytics, AI & Machine Learning, Finance & Web3, Infrastructurehttps://lowpaymentfee.com