x402-gated card-transactions endpoint on Base, pay-per-call with USDC.
What it does
This endpoint at lowpaymentfee.com exposes a card transactions resource at `/api/v1/cards/51/transactions` behind an x402 paywall. It accepts POST requests and is settled on the Base network using USDC (contract 0x8335…2913). The per-request cost is $0.02 (20,000 base units of USDC with 6 decimals). No API keys or rate limits are required — callers simply attach an X-PAYMENT header with a valid x402 payment proof.
The broader lowpaymentfee.com platform advertises a wide catalog of pay-per-call APIs spanning data analytics, AI/ML inference (sentiment analysis, 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. However, this specific listing covers only the `/api/v1/cards/51/transactions` endpoint, whose exact response payload and business logic are undocumented — the site's docs, pricing, and API pages all render only a "Connect wallet" prompt with no further detail.
Because there is no OpenAPI schema, no example request/response bodies, and no documentation beyond the landing page's brief catalog listing, the actual data returned by this endpoint is unknown. The endpoint is confirmed live (returns a proper 402 challenge), but callers should be aware that the functionality behind this particular path is opaque.
Capabilities
Use cases
- —Retrieving transaction data for a specific card via a single paid POST call
- —Integrating card transaction lookups into an agent workflow without API key management
- —Programmatic access to card transaction records settled via on-chain USDC micropayments
Fit
Best for
- —Agents that can settle x402 payments in USDC on Base
- —Developers wanting keyless, pay-per-use card transaction data
- —Workflows requiring low-friction, no-subscription API access
Not for
- —Users needing detailed API documentation or guaranteed SLAs before integrating
- —High-volume batch processing where $0.02/request adds up quickly
- —Anyone without a Base-compatible USDC wallet
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/cards/51/transactions \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>"Endpoint
Quality
The endpoint is confirmed live with a valid 402 challenge and clear pricing ($0.02 USDC on Base). However, there is no OpenAPI schema, no request/response examples, and no documentation explaining what the endpoint actually returns. The docs, pricing, and API pages are all blank beyond a wallet-connect prompt. The specific resource path (/cards/51/transactions) is not mentioned anywhere in the site's own catalog, making it unclear whether this is a real production endpoint or a demo stub.
Warnings
- —No documentation available — docs, pricing, and API pages render only 'Connect wallet' with no content.
- —The specific path /api/v1/cards/51/transactions is not listed in the site's own API catalog, raising questions about its purpose.
- —No request or response schema is provided; callers cannot know what data to send or expect back.
- —The broader site lists many diverse API categories (AI, finance, geocoding, etc.) all at the same price, which may indicate placeholder/demo endpoints rather than production services.
Citations
- —The endpoint returns a 402 challenge with x402Version 1, accepting USDC on Base network with maxAmountRequired of 20000 base units.https://lowpaymentfee.com/api/v1/cards/51/transactions
- —USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base.https://lowpaymentfee.com/api/v1/cards/51/transactions
- —The site advertises $0.02/request pricing with no API keys, no rate limits, and instant access on the Base network.https://lowpaymentfee.com
- —The docs, pricing, API, and README pages all render only a 'Connect wallet' prompt with no additional content.https://lowpaymentfee.com/docs