x402-payable 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 marketplace that exposes a broad set 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, paid in USDC on the Base network via the x402 protocol — no API keys, no rate limits, and no upfront commitments.
The specific endpoint being listed here (`/api/v1/carts/12`) is labeled "Premium API Access" and accepts POST requests. Its x402 challenge advertises a maxAmountRequired of 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02 given USDC's 6 decimals. Payment is settled on-chain to address 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3 with a 300-second timeout.
Documentation beyond the landing page is extremely thin — the /docs, /api, /pricing, and /README routes 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 crawled material. The purpose of the `/api/v1/carts/12` path specifically (as opposed to the other listed endpoints) is unclear; it may represent a shopping-cart or bundled-access resource, but this is speculative.
Capabilities
Use cases
- —Agents needing on-demand AI inference (sentiment, summarization, classification, embeddings) without API key management
- —Fetching real-time crypto token quotes and gas estimates via micropayment
- —Geocoding and data validation as a utility service paid per call
- —Exporting analytics data or generating reports with no subscription
Fit
Best for
- —AI agents that can settle x402 payments in USDC on Base
- —Developers wanting zero-signup, pay-per-use API access
- —Low-volume or bursty workloads where subscription pricing is wasteful
Not for
- —High-volume production workloads needing SLAs and guaranteed uptime
- —Users who cannot transact in USDC on the Base network
- —Applications requiring detailed API documentation or OpenAPI specs before integration
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/carts/12 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>" \
-d '{}'Example
Request
{
"url": "https://lowpaymentfee.com/api/v1/carts/12",
"body": {},
"method": "POST",
"headers": {
"X-PAYMENT": "<x402-payment-token>",
"Content-Type": "application/json"
}
}Endpoint
Quality
The endpoint is live (402 challenge captured) and pricing is clear ($0.02 USDC on Base), but there is no OpenAPI spec, no request/response schema, no documentation beyond a landing page, and the specific purpose of /api/v1/carts/12 is undocumented. Most site pages return only a 'Connect wallet' stub.
Warnings
- —No OpenAPI or schema documentation available for any endpoint
- —The /docs, /pricing, /api, and /README pages contain no useful content beyond 'Connect wallet'
- —The specific purpose of /api/v1/carts/12 ('Premium API Access') is unclear — it does not match any of the documented endpoint categories
- —No example responses are available; response format is unknown
- —Cannot verify that the advertised AI/finance/utility endpoints actually function as described
Citations
- —All endpoints priced at $0.02/request with no API keys, no rate limits, instant access on Base networkhttps://lowpaymentfee.com
- —Endpoint categories include Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructurehttps://lowpaymentfee.com
- —x402 challenge returns maxAmountRequired of 20000 base units of USDC (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Basehttps://lowpaymentfee.com/api/v1/carts/12
- —Payment address is 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3 with 300-second timeouthttps://lowpaymentfee.com/api/v1/carts/12