Pay-per-call API platform on Base (USDC) offering data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-enabled API platform that provides a broad catalog of pay-per-request endpoints settled in USDC on the Base network. The specific endpoint `/api/v1/inbox/5` is listed as "Premium API Access" and costs up to $0.02 per call (20,000 base units of USDC with 6 decimals). No API keys, rate limits, or subscriptions are required — callers simply attach an x402 payment header to each request.
The wider platform advertises four endpoint 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 listed endpoints share the same $0.02/request pricing.
The specific purpose of the `/api/v1/inbox/5` endpoint is not documented beyond the label "Premium API Access." There is no OpenAPI schema, no request/response examples, and the crawled docs pages (pricing, README, /api) returned only a "Connect wallet" prompt with no additional content. The endpoint is live and returns a valid x402 challenge, but the lack of documentation makes it difficult to know what payload to send or what response to expect.
Capabilities
Use cases
- —Programmatic access to a premium API endpoint with per-call USDC micropayments
- —Agent-driven workflows that need keyless, pay-as-you-go API access on Base
- —Exploring x402 payment protocol integrations with a low-cost test endpoint
Fit
Best for
- —Developers experimenting with x402 payment protocol
- —Agents that need keyless pay-per-call API access
- —Users who want to avoid subscriptions and pay only per request
Not for
- —Anyone needing well-documented API contracts with clear request/response schemas
- —High-volume use cases where per-call pricing may add up without volume discounts
- —Users who cannot transact in USDC on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/5 \
-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 request/response documentation, and the purpose of /api/v1/inbox/5 is entirely unclear beyond the generic label 'Premium API Access'. Crawled pages yielded almost no useful content. This is effectively a stub listing.
Warnings
- —No documentation available for /api/v1/inbox/5 — purpose, expected request body, and response format are unknown
- —No OpenAPI or schema definition found anywhere on the site
- —Crawled /pricing, /README, and /api pages returned only 'Connect wallet' with no content
- —The specific function of this endpoint cannot be verified — it may be a placeholder or test endpoint
Citations
- —The endpoint returns a valid x402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/inbox/5
- —All listed endpoints are priced at $0.02 per request with no API keys, rate limits, or minimumshttps://lowpaymentfee.com
- —The platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com
- —USDC asset address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base networkhttps://lowpaymentfee.com/api/v1/inbox/5