x402-gated product inventory endpoint on Base, pay-per-call with USDC.
What it does
This endpoint at lowpaymentfee.com provides access to a product inventory resource (product ID 21) via the x402 payment protocol. It is one of many endpoints offered by the lowpaymentfee.com platform, which hosts a variety of pay-per-request APIs spanning data analytics, AI/ML inference, finance, and utility services — all gated behind x402 micropayments settled in USDC on the Base network.
The specific endpoint `/api/v1/products/21/inventory` is labeled "Premium API Access" in the x402 challenge. It accepts POST requests and returns JSON. The maximum amount required per call is 20,000 base units of USDC (the asset at 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base, which uses 6 decimals), equating to $0.02 per request. The platform advertises no API keys, no rate limits, and instant access — callers simply attach an x402 payment header to each request.
Documentation is extremely sparse. The docs, API, pricing, and README pages all render only a "Connect wallet" prompt with no further content. There is no OpenAPI schema, no request/response examples, and no description of what the inventory data actually contains or what fields the POST body expects. The endpoint is confirmed live (returns a proper 402 challenge), but without documentation it is difficult to know what data is returned or what input parameters are accepted.
Capabilities
Use cases
- —Querying product inventory data for product ID 21 via micropayment
- —Integrating pay-per-request inventory checks into automated agent workflows
- —Demonstrating x402 protocol usage for commerce data access
Fit
Best for
- —Agents or developers experimenting with x402 micropayment protocol
- —Low-volume, on-demand inventory lookups without API key management
- —Crypto-native applications already operating on Base network
Not for
- —Production inventory management requiring documented schemas and SLAs
- —High-volume bulk inventory queries where per-request pricing is inefficient
- —Users who need detailed API documentation before integration
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/products/21/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 all documentation pages render only a wallet-connect prompt. The actual data returned by this inventory endpoint is completely undocumented, making it essentially a stub listing.
Warnings
- —No API documentation available — docs, pricing, and README pages all show only 'Connect wallet'
- —No OpenAPI or input/output schema provided; request body format is unknown
- —The purpose and content of 'product 21 inventory' is not described anywhere
- —No response examples available to verify what data is actually returned
Citations
- —The endpoint returns a 402 challenge with maxAmountRequired of 20000 base units of USDC on Base networkhttps://lowpaymentfee.com/api/v1/products/21/inventory
- —The platform advertises $0.02 per request, no API keys, no rate limits, instant access, Base networkhttps://lowpaymentfee.com
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/products/21/inventory
- —Documentation pages (docs, api, pricing, README) render only 'Connect wallet' with no further contenthttps://lowpaymentfee.com/docs