Pay-per-request API platform on Base via x402 — $0.02/call in USDC, no keys required.
What it does
lowpaymentfee.com is an x402-enabled API platform that offers a broad catalog of pay-per-request endpoints across data analytics, AI/ML inference, finance/Web3, and infrastructure utilities. Every endpoint costs $0.02 per request, paid in USDC on the Base network. There are no API keys, no rate limits, and no sign-up — callers simply attach an x402 payment header to each request.
The specific endpoint at `/api/v1/inbox/188` is listed as "Premium API Access" and accepts POST requests. Its x402 challenge advertises a maximum amount of 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02 given USDC's 6 decimals. The payment is settled on-chain to address 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3 with a 300-second timeout.
The broader platform 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. However, no OpenAPI schema, request/response examples, or detailed documentation were found during crawling; the docs, pricing, and README pages all resolve to a wallet-connect prompt with no further content. The exact functionality of the `/api/v1/inbox/188` endpoint specifically is unclear from available materials.
Capabilities
Use cases
- —Agents that need on-demand API access without pre-registration or API keys
- —Paying for individual AI inference calls (sentiment, summarization, classification) with USDC
- —Fetching real-time crypto quotes, gas estimates, or exchange rates per request
- —Geocoding or data validation as a utility microservice
Fit
Best for
- —AI agents and bots that can attach x402 payment headers automatically
- —Developers who want zero-friction, keyless API access on Base
- —Low-volume or bursty workloads where per-call pricing is preferable to subscriptions
Not for
- —High-volume production workloads where $0.02/request adds up quickly
- —Users who need detailed API documentation or guaranteed SLAs before integrating
- —Callers who cannot transact in USDC on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/188 \
-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), but there is no OpenAPI schema, no request/response examples, and no documentation beyond a landing page listing. The specific purpose of /api/v1/inbox/188 ('Premium API Access') is not explained anywhere. Docs, pricing, and README pages all resolve to a wallet-connect stub with no content.
Warnings
- —No OpenAPI or schema documentation available for any endpoint
- —The exact functionality of /api/v1/inbox/188 is undocumented — 'Premium API Access' is the only description
- —Docs, pricing, and README pages return only a wallet-connect prompt with no useful content
- —No request or response examples could be found or inferred
- —The broad catalog of endpoints listed on the homepage could not be individually verified
Citations
- —The endpoint returns a 402 x402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/inbox/188
- —USDC asset address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/inbox/188
- —All endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —The platform offers endpoints across Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com