x402-gated card transaction endpoint on Base, pay $0.02 per request in USDC.
What it does
This endpoint at lowpaymentfee.com provides access to a card transactions resource via the x402 payment protocol. The specific path `/api/v1/cards/21/transactions` suggests it returns or creates transaction records for a particular card (card ID 21). Payment is settled on the Base network using USDC (contract 0x8335…2913) at a cost of $0.02 per request (20,000 base units with 6 decimals).
The provider lowpaymentfee.com hosts a broader suite of x402-gated 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 advertised at $0.02 per request with no API keys, no rate limits, and instant access. However, the specific endpoint listed here falls under a "cards/transactions" path that is not explicitly documented on the provider's landing page.
The endpoint is live and returns a valid x402 challenge (HTTP 402) with version 1, accepting the "exact" payment scheme. The POST method is required. No OpenAPI schema, detailed request/response documentation, or usage examples were found in the crawled material — the docs, API, pricing, and README pages all rendered only a "Connect wallet" prompt with no substantive content.
Capabilities
Use cases
- —Retrieving or creating transaction records for a specific card via programmatic API calls
- —Integrating card transaction data into agent workflows that support x402 micropayments
- —Accessing financial card data without API keys using on-chain USDC payments
Fit
Best for
- —Agents or applications that can settle x402 payments in USDC on Base
- —Developers wanting keyless, pay-per-request access to card transaction data
- —Prototyping x402 payment flows with low per-call costs
Not for
- —Users who need detailed API documentation or OpenAPI schemas before integrating
- —Applications requiring free or subscription-based access without per-call crypto payments
- —Production systems needing guaranteed SLAs — no rate limit or uptime guarantees are documented
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/cards/21/transactions \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is live and returns a valid x402 challenge, but there is no OpenAPI schema, no request/response documentation, and no examples. The specific /cards/21/transactions path is not listed on the provider's landing page, and all documentation pages render only a wallet-connect prompt. The actual functionality behind this endpoint is unclear.
Warnings
- —The /api/v1/cards/21/transactions path is not listed among the provider's documented APIs — its purpose and expected input/output are unknown.
- —No OpenAPI spec, request schema, or response schema is available; integration requires guesswork.
- —All documentation pages (docs, API, pricing, README) returned only a 'Connect wallet' prompt with no substantive content.
- —The provider lists many diverse API categories (AI, finance, geocoding, etc.) all at the same price, which may indicate placeholder or demo endpoints rather than production services.
Citations
- —The endpoint returns a valid x402 challenge with maxAmountRequired of 20000 base units in USDC on Base network.https://lowpaymentfee.com/api/v1/cards/21/transactions
- —The provider advertises $0.02 per request pricing with no API keys, no rate limits, and instant access.https://lowpaymentfee.com
- —USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base.https://lowpaymentfee.com/api/v1/cards/21/transactions