Pay-per-call API platform on Base (USDC) covering data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-enabled API marketplace that exposes a broad set 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, payable in USDC on the Base network via the x402 protocol — no API keys, no rate limits, and no upfront commitments.
The specific endpoint at `/api/v1/inbox/52` is listed as "Premium API Access" and returns a valid x402 402 challenge with a maxAmountRequired of 20,000 base units of USDC (0x8335… on Base), which equals $0.02 given USDC's 6 decimals. Payment is sent to address 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3 using the "exact" scheme. The endpoint accepts HTTP POST and returns application/json.
Documentation beyond the landing page is sparse — the /api, /pricing, and /README routes all resolve to a wallet-connect prompt with no additional technical detail. There is no OpenAPI spec, no request/response schema documentation, and no example payloads available. The purpose of the `/inbox/52` path specifically (as opposed to the named category endpoints) is unclear; it may be a generic or catch-all premium endpoint. Agents should be aware that without input/output schemas, integration requires experimentation or out-of-band documentation.
Capabilities
Use cases
- —Agents needing on-demand AI inference (sentiment, summarization, classification, embeddings) without API key management
- —Fetching real-time crypto token quotes and gas estimates via micropayment
- —Geocoding and data validation as a utility service with no subscription
- —Exporting analytics data or generating reports on a per-request basis
- —Web3-native applications that want to pay for API calls in USDC on Base
Fit
Best for
- —AI agents that need keyless, pay-as-you-go access to diverse API categories
- —Developers prototyping with low-cost, no-commitment API calls
- —Web3 applications already operating on the Base network with USDC
Not for
- —High-volume production workloads needing guaranteed SLAs and detailed documentation
- —Users who need well-documented request/response schemas before integration
- —Teams that cannot transact in USDC on the Base L2 network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/52 \
-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 it accepts USDC payments on Base at $0.02/request. However, there is no OpenAPI spec, no request/response schema, no example payloads, and the specific purpose of /api/v1/inbox/52 is undocumented. The landing page lists many endpoints but provides no technical integration details beyond pricing.
Warnings
- —No OpenAPI or schema documentation available for any endpoint
- —The /api, /pricing, and /README pages all resolve to a wallet-connect prompt with no content
- —The specific purpose and expected input of /api/v1/inbox/52 ('Premium API Access') is unclear — it does not match any of the named category endpoints on the landing page
- —No example request or response payloads are documented anywhere
Citations
- —All endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —The x402 challenge for /api/v1/inbox/52 specifies maxAmountRequired of 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Basehttps://lowpaymentfee.com/api/v1/inbox/52
- —Available API categories include Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructurehttps://lowpaymentfee.com