Pay-per-call API platform on Base network — $0.02/request via x402 USDC payments.
What it does
lowpaymentfee.com is an x402-enabled API platform that offers a broad suite of endpoints spanning data analytics, AI/ML inference, finance/Web3 data, and infrastructure utilities. Every endpoint is priced at $0.02 per request, paid in USDC on the Base network with no API keys, rate limits, or subscriptions required. The x402 protocol handles payment inline: callers attach a payment header and the server fulfills the request upon verification.
The specific endpoint at `/api/v1/inbox/20` is listed as "Premium API Access" with a maximum charge of 20,000 base units of USDC (0.02 USD, since USDC uses 6 decimals). The payment is settled on-chain to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` using the USDC contract `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913` on Base. The endpoint accepts POST requests and returns `application/json`.
The broader platform advertises categories including metrics, reports, data export, insights, 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 are available for any of these endpoints, including this one. The purpose and input format of the `/api/v1/inbox/20` endpoint specifically is unclear from the available material.
Capabilities
Use cases
- —Accessing pay-per-call API services without subscriptions or API keys
- —Making micropayment-gated API requests settled in USDC on Base
- —Integrating x402-compatible endpoints into agent workflows
Fit
Best for
- —Developers wanting zero-commitment, pay-as-you-go API access
- —AI agents that can settle x402 payments autonomously
- —Users who prefer crypto-native micropayments over traditional billing
Not for
- —Users needing detailed API documentation or OpenAPI specs before integration
- —High-volume consumers who would benefit from bulk pricing or subscriptions
- —Anyone without access to USDC on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/20 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-header>" \
-d '{}'Endpoint
Quality
The endpoint is live (402 challenge confirmed) and pricing is clear ($0.02 USDC on Base). However, there is no OpenAPI schema, no documentation for the /inbox/20 endpoint specifically, no example requests or responses, and the purpose of this particular endpoint is entirely unclear. The crawled pages beyond the landing page returned only 'Connect wallet' with no useful content.
Warnings
- —No OpenAPI or schema documentation available for any endpoint
- —The specific purpose and expected input of /api/v1/inbox/20 is undocumented — 'Premium API Access' is a generic label
- —No example request or response payloads are available
- —Crawled /api, /pricing, and /README pages returned no meaningful content (only 'Connect wallet')
- —The platform lists many endpoint categories but none have detailed docs; actual functionality is unverifiable
Citations
- —Endpoint returns 402 with x402 challenge advertising USDC payment on Base networkhttps://lowpaymentfee.com/api/v1/inbox/20
- —All endpoints priced at $0.02 per request with no API keys, rate limits, or minimumshttps://lowpaymentfee.com
- —USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/inbox/20
- —Platform offers endpoints across data/analytics, AI/ML, finance/Web3, and infrastructure categorieshttps://lowpaymentfee.com