Pay-per-call API platform on Base (USDC) offering data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-enabled API platform that exposes a broad catalog of endpoints across four categories: 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 at $0.02 per request, settled in USDC on the Base network via the x402 protocol.
The specific endpoint `/api/v1/inbox/25` is listed as "Premium API Access" and returns a 402 challenge requesting up to 20,000 base units of USDC (0x8335…2913 on Base, 6 decimals = $0.02). Payment is made via the x402 exact scheme with no API keys, no rate limits, and no upfront commitments required. The endpoint accepts HTTP POST and returns application/json.
Documentation is extremely sparse — the /api, /pricing, and /README pages all resolve to a wallet-connect prompt with no further content. There is no OpenAPI spec, no request/response schema documentation, and no examples available. The purpose of the `/api/v1/inbox/25` endpoint specifically is unclear; it does not map to any of the named endpoints on the landing page. Without documentation it is impossible to determine what request body it expects or what response it produces.
Capabilities
Use cases
- —Agents that need on-demand AI inference (sentiment, summarization, classification, embeddings) without API key management
- —Fetching real-time financial data like token quotes, gas estimates, and exchange rates with per-call billing
- —Geocoding or data validation as a utility service paid in USDC on Base
Fit
Best for
- —Developers or agents wanting zero-commitment, pay-per-use API access
- —Crypto-native workflows that can settle in USDC on Base
- —Low-volume or bursty usage patterns where subscription pricing is wasteful
Not for
- —High-volume production workloads needing SLAs, rate-limit guarantees, or detailed documentation
- —Users who cannot transact in USDC on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/25 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>" \
-d '{}'Endpoint
Quality
The endpoint is live and returns a valid x402 402 challenge, confirming pricing and network. However, there is no OpenAPI spec, no request/response schema, no documentation beyond a landing page listing, and the specific /api/v1/inbox/25 path is not described anywhere on the site. The purpose and expected input/output of this endpoint are unknown.
Warnings
- —No OpenAPI or schema documentation available for any endpoint
- —The path /api/v1/inbox/25 does not correspond to any named endpoint on the landing page — its function is unclear
- —All documentation pages (/api, /pricing, /README) return only a wallet-connect prompt with no content
- —No request body schema or response examples are available anywhere
Citations
- —The endpoint returns a 402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/inbox/25
- —All listed endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —The platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com
- —USDC contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 with 6 decimalshttps://lowpaymentfee.com/api/v1/inbox/25