Pay-per-call premium API access on Base via x402 — $0.02/request in USDC.
What it does
lowpaymentfee.com offers a suite of pay-per-request API endpoints gated by the x402 protocol, settling payments in USDC on the Base network. The specific endpoint `/api/v1/keys/20` is listed as "Premium API Access" and costs up to $0.02 per call (maxAmountRequired of 20,000 base units of USDC, which is 6-decimal, equaling $0.02). No API keys, subscriptions, or rate limits are advertised — callers simply attach an X-PAYMENT header with a valid x402 payment proof.
The broader platform groups its endpoints into 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 listed at the same $0.02/request price point.
This particular endpoint (`/api/v1/keys/20`) does not have detailed documentation about its request or response schema beyond the x402 challenge. The probe confirms it is live, returning a proper 402 challenge with x402 version 1. The payment is directed to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` using USDC (`0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`) on Base. The endpoint accepts POST requests and has a payment timeout of 300 seconds.
Capabilities
Use cases
- —Programmatic access to premium API features without managing API keys or subscriptions
- —Agent-driven workflows that need on-demand, pay-as-you-go API calls settled in USDC
- —Accessing a broad set of data, AI, finance, and utility endpoints at low per-request cost
Fit
Best for
- —Developers or agents wanting zero-commitment, per-request API billing
- —x402-compatible clients on the Base network
- —Low-cost micropayment API consumption without rate limits
Not for
- —Users who need detailed API documentation or OpenAPI specs before integrating
- —High-volume consumers who would benefit from bulk pricing or subscriptions
- —Callers without USDC on Base or without x402 client support
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/keys/20 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>"Endpoint
Quality
The endpoint is confirmed live via a valid 402 x402 challenge, and pricing is clear ($0.02 USDC on Base). However, there is no OpenAPI spec, no request/response schema documentation, no examples, and the purpose of this specific endpoint ('Premium API Access' at /api/v1/keys/20) is vague. The crawled pages beyond the landing page returned only 'Connect wallet' with no useful content.
Warnings
- —No OpenAPI or schema documentation available for this endpoint
- —The exact functionality of /api/v1/keys/20 ('Premium API Access') is unclear — it may generate or return API keys, but this is unconfirmed
- —Crawled /api, /pricing, and /README pages returned no meaningful content beyond 'Connect wallet'
- —No example request or response bodies are available
Citations
- —Endpoint returns a valid x402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/keys/20
- —USDC contract address on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/keys/20
- —All listed endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —Platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com