x402-gated card transaction endpoint on Base, pay-per-call with USDC.
What it does
This endpoint at lowpaymentfee.com provides access to a card transactions resource at `/api/v1/cards/99/transactions` via the x402 payment protocol. The endpoint is live and returns a 402 challenge requiring payment in USDC on the Base network. The maximum amount required per call is 20,000 base units of USDC (6 decimals), which equals $0.02 per request.
The hosting site lowpaymentfee.com advertises a broad catalog of pay-per-call APIs spanning data & analytics, AI/ML (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 with no API keys, no rate limits, and instant access via the Base network. However, the specific endpoint being listed here (`/cards/99/transactions`) is not explicitly documented on the site's landing page among the advertised APIs, so its exact functionality is unclear.
The endpoint accepts POST requests and settles payments to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` using USDC (`0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`) on Base. No OpenAPI schema, detailed documentation, or example request/response bodies were found in the crawl. The docs, API, pricing, and README pages all returned only a "Connect wallet" prompt with no substantive content.
Capabilities
Use cases
- —Retrieving card transaction data for a specific card via pay-per-call
- —Integrating card transaction lookups into agent workflows without API key management
- —Programmatic access to transaction records settled via USDC on Base
Fit
Best for
- —Agents needing keyless, pay-per-call access to card transaction data
- —Developers experimenting with x402 payment protocol integrations
- —Workflows requiring on-demand transaction retrieval without subscriptions
Not for
- —Production use cases requiring documented request/response schemas
- —High-volume batch processing where per-call pricing is inefficient
- —Users who need detailed API documentation before integration
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/cards/99/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 no OpenAPI schema, no documentation of request/response formats, and the specific /cards/99/transactions path is not listed among the site's advertised APIs. The docs pages are empty beyond a wallet-connect prompt. Functionality must be entirely inferred.
Warnings
- —The /api/v1/cards/99/transactions endpoint is not listed among the site's advertised APIs — its purpose and expected input/output are unknown.
- —No API documentation, OpenAPI spec, or example payloads are available.
- —All documentation pages (docs, API, pricing, README) returned only a 'Connect wallet' prompt with no content.
- —The hardcoded card ID '99' in the path suggests this may be a demo or placeholder endpoint.
Citations
- —The endpoint returns a 402 challenge requiring USDC payment on Base with maxAmountRequired of 20000 base units ($0.02).https://lowpaymentfee.com/api/v1/cards/99/transactions
- —The site advertises all APIs at $0.02/request with no API keys, no rate limits, and instant access on Base network.https://lowpaymentfee.com
- —USDC asset address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 and payTo is 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3.https://lowpaymentfee.com/api/v1/cards/99/transactions