x402-gated API collection on Base — pay $0.02 per request in USDC, no keys required.
What it does
lowpaymentfee.com hosts a suite of x402-protocol pay-per-call APIs spanning data analytics, AI/ML inference, finance/Web3 data, and utility services. Every endpoint is gated by the x402 payment challenge: callers attach a USDC payment on the Base network in the X-PAYMENT header and receive the response immediately — no API keys, no accounts, no rate limits.
The specific endpoint `/api/v1/collections/25` is listed as "Premium API Access" and accepts POST requests. The x402 challenge advertises a maxAmountRequired of 20,000 base units of USDC (contract 0x8335…2913 on Base). Since USDC uses 6 decimals, this converts to $0.02 per request, consistent with the site's uniform $0.02 pricing across all endpoints.
The broader platform advertises endpoints in 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). Documentation pages beyond the landing page returned only a "Connect wallet" stub, so detailed request/response schemas, parameter descriptions, and example payloads are not available. The actual functionality behind `/api/v1/collections/25` is unclear — it may be a bundle or gateway to the listed collection of APIs, but this is not documented.
Capabilities
Use cases
- —AI agents making ad-hoc API calls without pre-registering for keys
- —Paying per request for sentiment analysis or text summarization
- —Fetching real-time crypto gas estimates or token quotes on demand
- —Running geocoding or data export tasks with instant USDC settlement
Fit
Best for
- —Developers or agents who want zero-signup, pay-as-you-go API access
- —Use cases requiring small, infrequent API calls where subscriptions are overkill
- —Crypto-native workflows that can attach x402 USDC payments on Base
Not for
- —High-volume production workloads where per-request crypto payments add overhead
- —Users without a Base-network USDC wallet or x402-compatible client
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/collections/25 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The x402 challenge is live and pricing is clear ($0.02 USDC on Base), but documentation pages are empty stubs ('Connect wallet' only). There is no OpenAPI spec, no request/response schema, no examples, and the purpose of the /collections/25 endpoint specifically is undocumented. The listing is essentially a stub with confirmed liveness.
Warnings
- —Documentation pages (/docs, /api, /pricing, /README) all return only 'Connect wallet' with no actual content.
- —No OpenAPI or schema available — request parameters and response format for /api/v1/collections/25 are unknown.
- —The purpose of '/collections/25' specifically (vs. individual endpoints like /ai/sentiment) is unclear; it may be a meta-endpoint or bundle.
- —No agents.txt or robots.txt found on the origin.
Citations
- —Uniform pricing of $0.02 per request across all endpoints, no API keys, no rate limitshttps://lowpaymentfee.com
- —x402 challenge returns maxAmountRequired of 20000 base units of USDC (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base networkhttps://lowpaymentfee.com/api/v1/collections/25
- —Available API categories include Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructurehttps://lowpaymentfee.com
- —Documentation pages return only 'Connect wallet' stub contenthttps://lowpaymentfee.com/docs