x402-payable card transactions endpoint on Base, settling in USDC at $0.02/request.
What it does
This endpoint at lowpaymentfee.com provides a POST-based card transactions API accessible via the x402 payment protocol. It is part of a broader platform offering dozens of pay-per-request endpoints spanning data analytics, AI/ML inference, finance/Web3 data, and infrastructure utilities — all priced at $0.02 per request and settled in USDC on the Base network.
The specific endpoint `/api/v1/cards/11/transactions` is labeled "Premium API Access" in the x402 challenge. The challenge advertises a maxAmountRequired of 20,000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913, which uses 6 decimals), equating to $0.02 per call. Payment is made via the x402 exact scheme with no API keys or rate limits required — callers simply attach an X-PAYMENT header with a valid payment proof.
Documentation is extremely sparse. The landing page lists available endpoints and pricing, but the /docs, /api, /pricing, and /README pages all render only a "Connect wallet" prompt with no further content. There is no OpenAPI spec, no request/response schema documentation, and no usage examples. The actual functionality behind the "cards/11/transactions" path is unclear — it could relate to financial card transaction data, but this is not confirmed anywhere in the crawled material. Prospective users should test the endpoint directly to understand its input requirements and output format.
Capabilities
Use cases
- —Retrieving card transaction data via a single paid API call
- —Integrating pay-per-request financial data into agent workflows
- —Testing x402 protocol payment flows on Base
Fit
Best for
- —Developers experimenting with x402 payment protocol
- —Agents needing on-demand card transaction lookups without API key management
- —Low-volume, pay-as-you-go API consumption
Not for
- —Users who need detailed API documentation before integrating
- —High-volume batch processing where per-request pricing adds up
- —Anyone requiring guaranteed SLAs or support
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/cards/11/transactions \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>"Endpoint
Quality
The endpoint is live (returns a valid 402 x402 challenge) and pricing is clear ($0.02/request in USDC on Base). However, there is no documentation, no OpenAPI spec, no request/response schema, and no examples. The actual purpose of the 'cards/11/transactions' path is undocumented. This is effectively a stub listing.
Warnings
- —No API documentation available — /docs, /pricing, /api, and /README pages all show only 'Connect wallet' with no content.
- —No OpenAPI or schema definition found; request body format and response structure are unknown.
- —The purpose of '/api/v1/cards/11/transactions' is not explained anywhere in the crawled material.
- —The platform lists many endpoints but none have documented schemas or examples.
Citations
- —The endpoint returns a 402 x402 challenge with maxAmountRequired of 20000 base units of USDC on Base networkhttps://lowpaymentfee.com/api/v1/cards/11/transactions
- —All endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —USDC asset address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/cards/11/transactions