Pay-per-request API platform on Base (USDC) via x402 — $0.02/call, no API keys required.
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, rate limits, or upfront commitments required. The platform advertises four categories of endpoints: 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).
The specific endpoint at `/api/v1/inbox/198` is labeled "Premium API Access" and returns a live x402 challenge requesting up to 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02 given USDC's 6 decimals. Payment is made via the `exact` scheme to wallet 0x1A2B…85F3 with a 300-second timeout. The endpoint accepts HTTP POST and returns `application/json`.
Note that the crawled documentation is extremely thin — the `/api`, `/pricing`, and `/README` pages all returned only a "Connect wallet" 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/198` path specifically is unclear; it does not match any of the advertised API categories listed on the homepage. Without documentation on expected request bodies or response formats, integration requires experimentation.
Capabilities
Use cases
- —Accessing data analytics and reports without API key management
- —Running AI inference (sentiment, summarization, classification, embeddings) on a per-request payment basis
- —Fetching real-time crypto and finance data (prices, gas estimates, exchange rates)
- —Using utility services like geocoding, validation, and conversion with instant pay-per-use
Fit
Best for
- —Developers who want zero-signup, pay-as-you-go API access
- —AI agents that can settle x402 payments autonomously on Base
- —Projects needing low-cost micro-transactions for API calls
Not for
- —Users who need detailed API documentation or guaranteed SLAs before integrating
- —High-volume consumers who would benefit from bulk pricing or subscription plans
- —Anyone unable to pay in USDC on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/198 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>" \
-d '{}'Endpoint
Quality
The endpoint is live and returns a valid x402 challenge, but there is no OpenAPI spec, no request/response schema, no examples, and the specific /api/v1/inbox/198 path is undocumented. The crawled docs pages are empty beyond a wallet-connect prompt. Effectively a stub listing.
Warnings
- —No OpenAPI or schema documentation available for any endpoint
- —The /api/v1/inbox/198 path does not match any of the advertised API categories on the homepage — its actual functionality is unknown
- —All documentation pages (/api, /pricing, /README) returned only 'Connect wallet' with no usable content
- —No request body or response body examples are available anywhere in the crawled material
Citations
- —The homepage lists four API categories (Data & Analytics, AI & ML, Finance & Web3, Infrastructure) each at $0.02/requesthttps://lowpaymentfee.com
- —Pricing is $0.02/request with no API keys, no rate limits, instant access on Base networkhttps://lowpaymentfee.com
- —x402 challenge returns maxAmountRequired of 20000 base units of USDC (6 decimals = $0.02) on Basehttps://lowpaymentfee.com/api/v1/inbox/198