Pay-per-call API platform on Base (USDC) via x402 — $0.02/request, no keys required.
What it does
lowpaymentfee.com is an x402-enabled API platform that offers a variety of endpoints across data analytics, AI/ML inference, finance/Web3 data, and infrastructure utilities. All endpoints are priced at $0.02 per request, paid in USDC on the Base network. The platform requires no API keys, no rate limits, and no upfront commitments — callers simply attach an x402 payment header to each request.
The specific endpoint `/api/v1/inbox/181` is listed as "Premium API Access" and returns a 402 challenge requesting up to 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02 given USDC's 6 decimals. The endpoint accepts POST requests and returns `application/json`. Payment is sent 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, detailed documentation, or example request/response payloads were found during the crawl. The exact functionality behind this particular inbox endpoint is unclear from available materials.
Capabilities
Use cases
- —Accessing premium API data without managing API keys or subscriptions
- —Making low-cost per-request API calls settled on Base L2 in USDC
- —Agent-driven workflows that need instant, keyless API access with crypto micropayments
Fit
Best for
- —Developers wanting zero-friction pay-as-you-go API access
- —AI agents that can settle x402 payments autonomously on Base
- —Projects needing low-cost API calls without subscription overhead
Not for
- —Users who need detailed API documentation or guaranteed SLAs before integrating
- —High-volume use cases where per-request pricing may not be cost-effective
- —Developers who cannot or prefer not to pay in crypto (USDC on Base)
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/181 \
-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, but there is no OpenAPI schema, no documentation, no example requests or responses, and the purpose of the specific '/api/v1/inbox/181' endpoint is entirely unclear. The broader site lists many endpoints but provides no detail on inputs, outputs, or behavior.
Warnings
- —No OpenAPI or schema documentation available for any endpoint
- —The specific function of /api/v1/inbox/181 ('Premium API Access') is not described anywhere in crawled materials
- —No example request or response payloads found — integration requires trial and error
- —Pricing and /README pages returned only 'Connect wallet' with no useful content
Citations
- —All endpoints priced at $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —x402 challenge requests maxAmountRequired of 20000 base units of USDC (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base, equaling $0.02https://lowpaymentfee.com/api/v1/inbox/181
- —Platform offers endpoints across Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com