x402-gated API endpoint on Base network, pay-per-request with USDC — no API keys required.
What it does
This endpoint at lowpaymentfee.com provides "Premium API Access" behind an x402 payment challenge. The specific resource `/api/v1/carts/98` accepts POST requests and charges up to 0.02 USDC per call (maxAmountRequired of 20000 in USDC's 6-decimal representation) on the Base network. Payment is made via the x402 "exact" scheme, settling to a specified wallet address using USDC (contract 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913).
The broader lowpaymentfee.com platform advertises a suite of pay-per-request APIs spanning 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 endpoints are listed at $0.02 per request with no API keys, no rate limits, and no commitments.
However, the specific endpoint `/api/v1/carts/98` is labeled only as "Premium API Access" with no further documentation on what it returns or what input it expects. The docs, pricing, and API pages on the site all render only a "Connect wallet" prompt with no additional content. There is no OpenAPI spec, no request/response schema, and no usage examples available from the crawl. The actual functionality behind this particular cart endpoint is unclear.
Capabilities
Use cases
- —Programmatic access to a pay-per-request API without needing API key registration
- —Agent-driven purchasing of API resources using on-chain USDC payments
- —Testing x402 payment protocol integrations against a live endpoint
Fit
Best for
- —Developers experimenting with x402 payment-gated APIs
- —Agents that can settle USDC payments on Base network
- —Users who want keyless, pay-as-you-go API access
Not for
- —Users who need detailed API documentation or guaranteed SLAs
- —Applications requiring free or fiat-only payment methods
- —Production workloads that need well-documented request/response contracts
Quick start
# The endpoint requires an X-PAYMENT header with a valid x402 payment proof.
curl -X POST https://lowpaymentfee.com/api/v1/carts/98 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The x402 challenge is live and well-formed, confirming the endpoint exists and accepts USDC on Base. However, there is no documentation, no OpenAPI spec, no request/response schema, and no explanation of what '/api/v1/carts/98' actually does. The docs pages are empty ('Connect wallet' only). The listing is effectively a stub with payment metadata but no functional specification.
Warnings
- —No documentation available — docs, pricing, and API pages all render only 'Connect wallet'
- —No OpenAPI or request/response schema provided for this endpoint
- —The purpose and output of /api/v1/carts/98 ('Premium API Access') is entirely undocumented
- —Cannot verify what data or service is actually returned after payment
Citations
- —Endpoint returns HTTP 402 with x402 challenge requiring USDC payment on Base networkhttps://lowpaymentfee.com/api/v1/carts/98
- —maxAmountRequired is 20000 (0.02 USDC) using exact schemehttps://lowpaymentfee.com/api/v1/carts/98
- —USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/carts/98
- —Platform advertises $0.02/request pricing with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —Platform lists APIs across data/analytics, AI/ML, finance/Web3, and infrastructure categorieshttps://lowpaymentfee.com