x402-gated card-transactions endpoint on Base, pay $0.02 per request in USDC.
What it does
This endpoint at lowpaymentfee.com exposes a POST resource at `/api/v1/cards/45/transactions` behind an x402 payment challenge. It is part of a broader platform that offers dozens of pay-per-call APIs spanning data analytics, AI/ML inference, finance/Web3 data, and infrastructure utilities — all priced at $0.02 per request, settled in USDC on the Base network.
The specific endpoint probed (`/api/v1/cards/45/transactions`) is labeled "Premium API Access" in the x402 challenge. Its exact functionality is not documented beyond the title; the path suggests it returns or creates transactions associated with a card resource (card ID 45). No request body schema or response schema is published, and the site's docs, pricing, and API pages all render only a "Connect wallet" prompt with no further detail.
The x402 challenge confirms the endpoint is live, accepting POST requests, and requires a payment of up to 20,000 base units of USDC (0x8335…on Base, 6 decimals) — i.e., $0.02 per call. Payment is sent to `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` with a 300-second timeout. No API keys or rate limits are advertised. Because there is no OpenAPI spec, no request/response examples, and no documentation beyond the landing page listing, the actual behavior of this endpoint remains opaque.
Capabilities
Use cases
- —Fetching or creating card transaction records via a single paid POST call
- —Integrating pay-per-use card data into agent workflows without API keys
- —Programmatic access to card-level transaction data settled in USDC on Base
Fit
Best for
- —Agents that can settle x402 USDC payments on Base
- —Developers wanting keyless, pay-per-call access to card transaction data
- —Prototyping micropayment-gated API integrations
Not for
- —Users who need detailed API documentation or response schemas before integrating
- —High-volume batch processing where per-call pricing is impractical
- —Anyone without a Base-compatible USDC wallet
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/cards/45/transactions \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-header>"Endpoint
Quality
The endpoint is live and returns a valid x402 challenge, but there is zero documentation on request/response schemas, no OpenAPI spec, and the docs/pricing/API pages are empty beyond a wallet-connect prompt. The purpose of this specific endpoint is unclear beyond its path and title.
Warnings
- —No request or response schema is published; actual endpoint behavior is unknown.
- —Docs, pricing, and API pages render only 'Connect wallet' with no usable content.
- —The endpoint path references a specific card ID (45) — unclear if this is a demo or production resource.
- —No OpenAPI or machine-readable specification available.
Citations
- —The endpoint returns a 402 x402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/cards/45/transactions
- —All APIs on the platform are priced at $0.02 per request with no API keys, no rate limits, and instant access on the Base networkhttps://lowpaymentfee.com
- —The USDC asset address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/cards/45/transactions