Pay-per-call API platform on Base (USDC) covering data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-enabled API platform that offers a broad catalog of pay-per-request endpoints settled in USDC on the Base network. The specific endpoint at `/api/v1/inbox/137` is listed as "Premium API Access" and costs up to $0.02 per call (20,000 base units of USDC with 6 decimals). Payment is handled via the x402 protocol — no API keys, accounts, or rate limits are required; callers simply attach an X-PAYMENT header with a valid payment proof.
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.
Important caveat: the specific `/api/v1/inbox/137` path does not correspond to any of the named endpoints on the landing page, and no documentation, OpenAPI schema, or example request/response payloads are available for it. The crawled docs, pricing, and README pages all returned only a "Connect wallet" prompt with no additional content. Without further documentation it is unclear what this particular inbox endpoint accepts or returns.
Capabilities
Use cases
- —Programmatic access to data analytics, AI inference, or financial data without managing API keys or subscriptions
- —Agent-driven workflows that need on-demand API calls settled instantly in USDC on Base
- —Prototyping or low-volume usage where flat per-request pricing avoids commitment
Fit
Best for
- —Developers or agents wanting zero-signup, pay-as-you-go API access
- —x402-compatible agent wallets on the Base network
- —Low-volume or bursty workloads where $0.02/request is cost-effective
Not for
- —High-volume production workloads where per-request costs add up quickly
- —Users who need detailed API documentation, SLAs, or guaranteed uptime
- —Callers without a Base-network USDC wallet or x402-compatible client
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/137 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402_payment_proof>" \
-d '{}'Endpoint
Quality
The endpoint is live (returns a valid 402 x402 challenge) and pricing is clear ($0.02 USDC on Base). However, there is no OpenAPI schema, no documentation for the /inbox/137 path specifically, no example request or response bodies, and the crawled pages beyond the landing page were empty. The endpoint's actual functionality is unknown.
Warnings
- —No documentation or schema available for /api/v1/inbox/137 — its purpose is unclear
- —The /inbox/137 path does not match any named endpoint on the provider's landing page
- —No OpenAPI spec, README content, or example payloads were found
- —Pricing, docs, and README pages returned only 'Connect wallet' with no useful content
Citations
- —The endpoint returns a valid x402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/inbox/137
- —All listed endpoints cost $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/inbox/137
- —Platform offers endpoints in Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com