Pay-per-request API platform on Base network via x402 — $0.02/call for data, AI, finance, and utility endpoints.
What it does
lowpaymentfee.com is an x402-enabled API platform that offers a collection of endpoints spanning data analytics, AI/ML inference, finance/Web3 data, and infrastructure utilities. All endpoints are pay-per-request using the x402 protocol, settling payments in USDC on the Base network. There are no API keys, no rate limits, and no minimum commitments — callers simply attach an X-PAYMENT header with each request.
The specific endpoint at `/api/v1/carts/99` is listed as "Premium API Access" and requires up to 20,000 units of USDC (0.02 USDC given 6 decimals) per call. The platform also advertises endpoints for sentiment analysis, text summarization, classification, embeddings, price feeds, exchange rates, token quotes, gas estimates, geocoding, validation, conversion, and generation — all at the same $0.02 price point. The x402 challenge was successfully captured, confirming the endpoint is live and accepting POST requests.
Documentation beyond the landing page is extremely thin — the /docs, /api, /pricing, and /README pages all returned only a "Connect wallet" prompt with no substantive content. There is no OpenAPI spec, no request/response schema documentation, and no usage examples available from the crawl. The actual behavior and response format of `/api/v1/carts/99` is unclear from available materials.
Capabilities
Use cases
- —Agents that need on-demand AI inference (sentiment, summarization, classification) without managing API keys
- —Fetching real-time crypto quotes, gas estimates, or exchange rates with per-call payment
- —Geocoding or data validation as a utility service paid in USDC on Base
- —Exporting data or generating analytics reports via pay-as-you-go endpoints
Fit
Best for
- —Developers or agents wanting zero-signup, pay-per-call API access
- —Use cases requiring USDC micropayments on Base L2
- —Prototyping or low-volume usage where subscription plans are overkill
Not for
- —High-volume production workloads needing SLAs or guaranteed uptime documentation
- —Users who need detailed API documentation, request/response schemas, or error handling guides
- —Anyone unable to transact in USDC on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/carts/99 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The x402 challenge is live and confirms the endpoint accepts POST with USDC on Base at ~$0.02. However, there is no OpenAPI spec, no request/response schema, no documentation beyond a landing page listing, and the specific purpose of /api/v1/carts/99 is unclear. The docs, pricing, and README pages are all empty wallet-connect stubs.
Warnings
- —No OpenAPI or schema documentation available — request/response formats are unknown
- —All documentation pages (/docs, /api, /pricing, /README) returned only 'Connect wallet' with no content
- —The specific endpoint /api/v1/carts/99 is labeled 'Premium API Access' but its actual function is undocumented
- —Cannot verify what data or service this specific endpoint returns
Citations
- —The endpoint returns a 402 challenge with x402Version 1, accepting USDC on Base network with maxAmountRequired of 20000 (0.02 USDC)https://lowpaymentfee.com/api/v1/carts/99
- —The platform advertises $0.02/request pricing with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —Available API categories include Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructurehttps://lowpaymentfee.com
- —Payment is made to address 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3 using USDC contract 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/carts/99