x402-gated product inventory API on Base, pay-per-request with USDC.
What it does
This endpoint at lowpaymentfee.com provides access to a product inventory resource (product ID 4) behind an x402 paywall. It accepts HTTP POST requests and returns JSON. Payment is settled on the Base network using USDC (contract 0x8335…2913) via the x402 "exact" scheme.
The specific endpoint `/api/v1/products/4/inventory` is listed as "Premium API Access" by the provider. The x402 challenge indicates a maximum required payment of 20,000 base units of USDC. Since USDC uses 6 decimals, this translates to $0.02 per request — consistent with the provider's site-wide pricing of $0.02/request across all their APIs. The provider advertises no API keys, no rate limits, and instant access.
The provider (lowpaymentfee.com) hosts a broader catalog of x402-gated APIs spanning data/analytics, AI/ML (sentiment, summarization, classification, embeddings), finance/Web3 (price feeds, exchange rates, token quotes, gas estimates), and infrastructure utilities (geocoding, validation, conversion, generation). However, this specific listing covers only the `/api/v1/products/4/inventory` endpoint. Documentation beyond the landing page is extremely thin — the docs, API, pricing, and README pages all render only a "Connect wallet" prompt with no further content. No OpenAPI schema, request/response examples, or detailed field documentation were found.
Capabilities
Use cases
- —Querying real-time product inventory data for product ID 4
- —Integrating inventory checks into automated agent workflows that can settle USDC on Base
- —Demonstrating x402 protocol payment flows for commerce APIs
Fit
Best for
- —Agents or applications that can settle x402 payments in USDC on Base
- —Developers exploring x402 pay-per-request API patterns
- —Low-volume, on-demand inventory lookups without subscription commitments
Not for
- —Users who need detailed API documentation or response schema before integrating
- —High-volume inventory queries where per-request pricing may add up
- —Applications that cannot settle crypto payments on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/products/4/inventory \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is live and returns a valid x402 challenge with clear pricing ($0.02 USDC on Base). However, there is no OpenAPI schema, no request/response examples, and no meaningful documentation — the docs/pricing/README pages are all blank beyond a wallet-connect prompt. The purpose of 'product inventory for product 4' is vague with no field-level detail.
Warnings
- —No OpenAPI or schema documentation available for this endpoint
- —Docs, pricing, API, and README pages all render only 'Connect wallet' with no content
- —The specific meaning of 'products/4/inventory' is unclear — no field or response structure documented
- —No example responses available to verify what data is actually returned
Citations
- —The endpoint returns a 402 x402 challenge with maxAmountRequired of 20000 USDC base units on Base networkhttps://lowpaymentfee.com/api/v1/products/4/inventory
- —Site-wide pricing is $0.02 per request with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/products/4/inventory