x402-gated product inventory endpoint on Base, paid per-request in USDC.
What it does
This endpoint at lowpaymentfee.com exposes a product inventory resource at `/api/v1/products/9/inventory` behind an x402 paywall. It accepts POST requests and returns JSON. Payment is settled on the Base network using USDC (contract 0x8335…2913) via the x402 "exact" scheme. The maximum amount required per call is 20,000 base units of USDC, which equals $0.02 (USDC uses 6 decimals).
The hosting site lowpaymentfee.com advertises a broad catalog of pay-per-call APIs spanning data analytics, AI/ML inference, finance/Web3 data, and infrastructure utilities — all priced at $0.02 per request with no API keys, no rate limits, and no commitments. However, this specific endpoint (`/products/9/inventory`) is labeled only as "Premium API Access" and is not listed among the documented API categories on the landing page. No OpenAPI spec, request/response schema, or detailed documentation was found for this endpoint. The docs, pricing, and README pages all returned minimal content (just a "Connect wallet" prompt).
Because the endpoint returned a well-formed 402 challenge with valid x402 v1 fields, it is confirmed live. But without documentation on what the inventory resource actually returns, what POST body it expects, or what "product 9" refers to, the practical utility for an agent is limited. Treat this as a low-documentation endpoint whose behavior must be discovered empirically after payment.
Capabilities
Use cases
- —Querying inventory status for a specific product behind a micropayment wall
- —Programmatic inventory checks by AI agents with USDC on Base
- —Exploring x402 protocol integration for pay-per-request commerce APIs
Fit
Best for
- —Developers experimenting with x402 payment protocol
- —Agents that can settle USDC payments on Base L2
- —Low-cost per-request inventory lookups without API key management
Not for
- —Production inventory management requiring documented schemas and SLAs
- —Users who need free or subscription-based API access
- —Applications requiring detailed product catalog browsing (only product 9 is exposed here)
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/products/9/inventory \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is live and returns a valid x402 challenge, confirming it works at the protocol level. However, there is no OpenAPI spec, no request/response schema, no documentation beyond a generic label, and the specific endpoint is not listed in the site's own catalog. Practical usability is very limited without knowing what to POST or what the response looks like.
Warnings
- —No documentation found for this specific endpoint (/api/v1/products/9/inventory)
- —Endpoint not listed among the site's advertised API catalog
- —No request body schema or response schema available
- —Docs, pricing, and README pages returned only 'Connect wallet' with no useful content
- —Purpose of 'product 9 inventory' is unknown — could be a demo or placeholder
Citations
- —The endpoint returns a 402 challenge with x402 v1 protocol, exact scheme, on Base network using USDC at 20000 base unitshttps://lowpaymentfee.com/api/v1/products/9/inventory
- —The site advertises $0.02 per request pricing with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/products/9/inventory