Pay-per-call API platform on Base network — $0.02/request via x402 USDC payments.
What it does
lowpaymentfee.com is a pay-per-request API platform that gates access to a collection of endpoints behind x402 micropayments settled in USDC on the Base network. The specific endpoint `/api/v1/inbox/16` is listed as "Premium API Access" and accepts POST requests with a maximum cost of 20,000 base units of USDC (i.e., $0.02 per call, since USDC uses 6 decimals). No API keys, rate limits, or upfront commitments are required — callers simply attach an x402 payment header to each request.
The broader platform advertises four categories of APIs: 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 listed endpoints share the same $0.02/request pricing. However, the specific functionality behind `/api/v1/inbox/16` is not documented beyond the label "Premium API Access," so its exact input/output behavior is unclear.
Payments are made to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` using the USDC contract `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913` on Base. The x402 challenge specifies a 300-second payment timeout and returns `application/json` responses.
Capabilities
Use cases
- —Accessing premium API endpoints without API key registration
- —Making micropayment-gated API calls from autonomous agents
- —Paying per request for data or utility services on Base network
Fit
Best for
- —Agents or developers wanting zero-signup API access
- —Micropayment use cases where $0.02/call is cost-effective
- —x402-compatible clients on the Base L2 network
Not for
- —Users who need detailed documentation or OpenAPI specs before integrating
- —High-volume callers who would benefit from bulk pricing or subscriptions
- —Callers who cannot settle payments in USDC on Base
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/16 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>" \
-d '{}'Endpoint
Quality
The endpoint is live (402 challenge confirmed) and pricing is clear ($0.02 USDC on Base), but there is no documentation of what /api/v1/inbox/16 actually does, no request/response schema, no OpenAPI spec, and the crawled pages beyond the homepage returned only 'Connect wallet' with no useful content. The endpoint's purpose is essentially unknown.
Warnings
- —No documentation exists for the specific endpoint /api/v1/inbox/16 — its functionality is unknown beyond the label 'Premium API Access'
- —No OpenAPI or request/response schema is available for any endpoint on the platform
- —The /api, /pricing, and /README pages returned no meaningful content (only 'Connect wallet')
- —The broad category labels (AI, Finance, etc.) on the homepage cannot be verified as functional
Citations
- —The endpoint returns a 402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/inbox/16
- —All listed endpoints are priced at $0.02 per request with no API keys, rate limits, or minimumshttps://lowpaymentfee.com
- —The platform advertises APIs across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com
- —USDC contract address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base networkhttps://lowpaymentfee.com/api/v1/inbox/16