Pay-per-call API platform on Base network — $0.02/request via x402 with USDC.
What it does
lowpaymentfee.com is a pay-per-request API platform that gates access to a broad set of endpoints using the x402 payment protocol. Each call costs $0.02 in USDC on the Base network, with no API keys, no rate limits, and no subscriptions required. The specific endpoint `/api/v1/inbox/120` is listed as "Premium API Access" and follows the same x402 payment pattern.
The 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 priced uniformly at $0.02 per request.
The probed endpoint at `/api/v1/inbox/120` returned a valid x402 challenge with `maxAmountRequired` of 20000 base units of USDC (0x8335… on Base), which equals $0.02 given USDC's 6 decimals. Payment is made via the `exact` scheme to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3`. The endpoint accepts POST requests and returns `application/json`. Note: the specific functionality behind the `/api/v1/inbox/120` path is not documented on the site — it does not appear in the listed API catalog, so its exact purpose is unclear.
Capabilities
Use cases
- —Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without subscriptions
- —Fetching real-time financial data like token quotes, exchange rates, and gas estimates
- —Running utility operations like geocoding, validation, and data conversion on demand
- —Exporting analytics data and generating reports with per-request billing
Fit
Best for
- —Agents or developers who want instant API access without signup or API keys
- —Low-volume or bursty workloads where per-request pricing is more economical than subscriptions
- —Crypto-native applications that can pay with USDC on Base
Not for
- —High-volume production workloads where per-request costs add up quickly
- —Users who cannot transact in USDC on the Base network
- —Applications requiring detailed documentation or SLAs — docs are minimal
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/120 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>" \
-d '{}'Endpoint
Quality
The x402 challenge is live and pricing is clear ($0.02 USDC on Base). However, the specific endpoint /api/v1/inbox/120 is not documented anywhere on the site, there is no OpenAPI schema, no request/response examples, and the crawled docs/pricing/README pages returned only 'Connect wallet' with no useful content. The endpoint's actual functionality is unknown.
Warnings
- —The endpoint /api/v1/inbox/120 does not appear in the site's listed API catalog — its specific functionality is undocumented.
- —No OpenAPI spec, request schema, or response schema is available.
- —The /pricing, /api, and /README pages returned no meaningful content (only 'Connect wallet').
- —The breadth of advertised APIs (AI, finance, analytics, utilities) could not be independently verified — only the x402 challenge on this single endpoint was confirmed live.
Citations
- —The platform advertises $0.02 per request with no API keys, no rate limits, and instant access on the Base network.https://lowpaymentfee.com
- —The x402 challenge for /api/v1/inbox/120 specifies maxAmountRequired of 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base.https://lowpaymentfee.com/api/v1/inbox/120
- —Listed API categories include Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructure.https://lowpaymentfee.com