x402-gated API platform on Base offering data, AI, finance, and utility endpoints at $0.02/request via USDC.
What it does
lowpaymentfee.com is an x402-protocol API marketplace that gates a broad set of endpoints behind per-request USDC micropayments on the Base network. The specific endpoint at `/api/v1/inbox/186` 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 made via the x402 exact scheme — no API keys, no rate limits, and no subscriptions required.
The provider's landing page advertises four categories of endpoints: 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 the `/api/v1/inbox/186` path is not documented — the name "Premium API Access" is generic and no input/output schema beyond `POST application/json` is provided.
The endpoint is live and returns a valid x402 challenge (HTTP 402) with payment directed to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` using USDC (`0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`) on Base. The maximum timeout is 300 seconds. Because no OpenAPI spec, request schema, or response examples are available, agents will need to experiment or rely on additional documentation to determine what this specific inbox endpoint actually does.
Capabilities
Use cases
- —Paying per-request for API access without subscriptions or API keys
- —Integrating x402-compatible agents with utility or data endpoints
- —Accessing AI, finance, or infrastructure services via crypto micropayments
Fit
Best for
- —Agents or developers wanting zero-signup, pay-per-call API access
- —x402-native workflows that settle payments on Base in USDC
- —Low-volume or sporadic API usage where $0.02/call is economical
Not for
- —High-volume production workloads where per-call pricing adds up quickly
- —Users who need detailed API documentation or guaranteed SLAs before integrating
- —Non-crypto workflows that cannot produce x402 payment headers
Quick start
# The endpoint requires an x402 X-PAYMENT header with a USDC payment proof on Base.
# Using curl as a conceptual example (actual payment header must be constructed per x402 spec):
curl -X POST https://lowpaymentfee.com/api/v1/inbox/186 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>" \
-d '{}'Endpoint
Quality
The endpoint is live and returns a valid x402 challenge, but the specific functionality of /api/v1/inbox/186 is completely undocumented — no input schema, no output schema, no examples, and the name 'Premium API Access' is generic. The broader site lists many endpoints but provides no detailed docs for any of them. This is effectively a stub listing.
Warnings
- —The specific functionality of /api/v1/inbox/186 is unknown — 'Premium API Access' is not descriptive
- —No OpenAPI spec, request schema, or response examples are available for any endpoint on the site
- —The /api, /pricing, and /README pages all returned only 'Connect wallet' with no useful content
- —Cannot verify that any of the advertised AI/data/finance endpoints actually function as described
Citations
- —The endpoint returns a valid x402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/inbox/186
- —All listed endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —The site advertises Data & Analytics, AI & ML, Finance & Web3, and Infrastructure endpoint categorieshttps://lowpaymentfee.com
- —USDC contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 with 6 decimalshttps://lowpaymentfee.com/api/v1/inbox/186