x402-gated card-transaction 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/20/transactions` behind the x402 payment protocol. It accepts POST requests and requires an X-PAYMENT header carrying a USDC payment on the Base network. The x402 challenge advertises a maximum cost of 20,000 base units of USDC (0x8335…), which at 6 decimals equals $0.02 per request.
The provider's landing page lists a broad catalog of pay-per-call APIs spanning data & analytics, AI/ML inference (sentiment, summarization, classification, embeddings), finance & Web3 (price feeds, exchange rates, token quotes, gas estimates), and infrastructure utilities (geocoding, validation, conversion, generation) — all priced at $0.02 per request with no API keys, no rate limits, and no commitments. However, the specific endpoint being listed here (`/api/v1/cards/20/transactions`) is not explicitly documented on the landing page, and no request/response schema or documentation beyond the x402 challenge was found. The docs, API, pricing, and README pages all returned only a "Connect wallet" prompt with no substantive content.
Because there is no OpenAPI spec, no example payloads, and no documentation describing what this particular endpoint accepts or returns, its exact functionality remains unclear. The endpoint is confirmed live (returns a well-formed 402 challenge), but consumers should expect to experiment or contact the provider for integration details.
Capabilities
Use cases
- —Submitting or querying card transaction data via a pay-per-call model
- —Integrating card transaction processing into agent workflows without API keys
- —Programmatic access to card-level transaction records gated by crypto micropayments
Fit
Best for
- —Developers wanting keyless, pay-per-call card transaction access
- —AI agents that can settle x402 payments on Base with USDC
- —Prototyping integrations where traditional API-key onboarding is undesirable
Not for
- —Production use cases requiring documented request/response schemas
- —High-volume batch processing where per-call pricing is inefficient
- —Users who cannot settle USDC payments on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/cards/20/transactions \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is confirmed live via a valid x402 402 challenge, but there is no OpenAPI spec, no request/response schema, no documentation, and the specific /cards/20/transactions path is not mentioned on the provider's own landing page. Functionality must be guessed.
Warnings
- —No documentation found for this specific endpoint — the /docs, /api, /pricing, and /README pages are all empty (just 'Connect wallet')
- —The /api/v1/cards/20/transactions path does not appear in the provider's listed API catalog on the landing page
- —No request body schema or response schema is available; integration requires experimentation
- —The broad API catalog on the landing page may be placeholder/demo content — all endpoints share identical $0.02 pricing and generic names
Citations
- —The x402 challenge advertises maxAmountRequired of 20000 base units of USDC on Base networkhttps://lowpaymentfee.com/api/v1/cards/20/transactions
- —The provider lists APIs at $0.02/request with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —USDC asset address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/cards/20/transactions