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-enabled API platform that exposes a broad catalog of endpoints across four categories: Data & Analytics (metrics, reports, 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, payable in USDC on the Base network via the x402 payment protocol — no API keys, no rate limits, and no upfront commitments.
The specific endpoint being listed here is `/api/v1/carts/72`, described by the provider as "Premium API Access." The x402 challenge confirms it is live and accepts POST requests, requiring up to 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02. Payment is made via the `exact` scheme to address 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3 with a 300-second timeout.
Documentation beyond the landing page is extremely thin — the /docs, /api, /pricing, and /README pages all render only a "Connect wallet" prompt with no additional technical detail. There is no OpenAPI spec, no request/response schema documentation, and no examples for any endpoint. The purpose of the `/api/v1/carts/72` path specifically is unclear; it does not appear in the site's listed catalog, which raises questions about whether it is a shopping-cart resource, a meta-endpoint, or something else entirely. Agents should treat this endpoint with caution until more documentation is available.
Capabilities
Use cases
- —Programmatic access to a pay-per-call API without needing API keys or subscriptions
- —Agent-driven workflows that settle per-request costs in USDC on Base
- —Exploring x402 protocol integration with a low-cost test endpoint
Fit
Best for
- —Developers experimenting with x402 payment flows
- —AI agents that need keyless, pay-as-you-go API access
- —Projects wanting sub-cent-level micropayment API consumption on Base
Not for
- —Production workloads requiring well-documented request/response schemas
- —Users who need fiat-only payment options (endpoint requires on-chain USDC on Base)
- —Anyone needing the specific catalog endpoints (this listing is for /carts/72, not the broader catalog)
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/carts/72 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-header>"Endpoint
Quality
The endpoint is live (402 challenge confirmed) and pricing is clear ($0.02 USDC on Base), but there is no OpenAPI spec, no request/response schema, no documentation beyond a wallet-connect prompt, and the specific /carts/72 path is not listed in the site's own catalog. Effectively a stub listing.
Warnings
- —The /api/v1/carts/72 endpoint does not appear in the provider's own catalog of available APIs — its purpose is undocumented.
- —All documentation pages (/docs, /api, /pricing, /README) return only a 'Connect wallet' prompt with no technical content.
- —No OpenAPI spec, no request/response examples, and no output schema beyond the x402 challenge metadata.
- —The broader catalog advertises many endpoints but none have documented schemas or example payloads.
Citations
- —All endpoints priced at $0.02/request with no API keys, no rate limits, on Base networkhttps://lowpaymentfee.com
- —x402 challenge returns maxAmountRequired of 20000 base units of USDC (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base, equaling $0.02https://lowpaymentfee.com/api/v1/carts/72
- —Catalog includes Data & Analytics, AI & ML, Finance & Web3, and Infrastructure endpoint categorieshttps://lowpaymentfee.com
- —Documentation pages render only a Connect wallet prompthttps://lowpaymentfee.com/docs