x402-payable card transaction endpoint on Base, settling in USDC at $0.02 per 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 data & analytics, AI/ML inference, finance/Web3, and infrastructure utility endpoints—all priced at $0.02 per request with no API keys, no rate limits, and no commitments required.
The specific endpoint `/api/v1/cards/43/transactions` is labeled "Premium API Access" in the x402 challenge. Payment settles on the Base network using USDC (contract 0x8335…2913). The challenge advertises a maxAmountRequired of 20,000 base units; since USDC uses 6 decimals, this equals $0.02 per call, consistent with the site's published pricing. The x402 challenge version is 1, scheme is "exact", and the endpoint accepts POST requests.
Documentation is extremely sparse—the /docs, /api, /pricing, and /README pages all render only a "Connect wallet" prompt with no further technical detail. There is no OpenAPI spec, no request/response schema documentation, and no example payloads available. The endpoint name suggests it deals with card transactions (possibly virtual card or payment card data), but the actual request body format and response structure are unknown. Agents should treat this as a stub listing until more documentation surfaces.
Capabilities
Use cases
- —Submitting or querying card transactions via a pay-per-request model
- —Integrating card transaction processing into agent workflows without API key management
- —Programmatic access to card transaction data settled via USDC on Base
Fit
Best for
- —Agents needing keyless, pay-per-call card transaction access
- —Developers experimenting with x402 protocol integrations
- —Use cases requiring low-friction micropayment-gated API access
Not for
- —Production workloads requiring documented request/response schemas
- —Users who need detailed API documentation or SDKs before integration
- —High-volume batch processing where per-request pricing may not be optimal
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/cards/43/transactions \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>" \
-d '{}'Endpoint
Quality
The endpoint is live (402 challenge captured) and pricing is clear ($0.02/request in USDC on Base). However, there is no OpenAPI spec, no request/response schema, no documentation beyond a wallet-connect prompt, and the endpoint's actual functionality (what 'cards/43/transactions' does) is undocumented. This is effectively a stub.
Warnings
- —No API documentation available—/docs, /api, /pricing, and /README pages all show only 'Connect wallet'
- —No OpenAPI or schema definition found; request body format and response structure are completely unknown
- —The purpose of 'cards/43/transactions' is unclear—'Premium API Access' is a generic label with no functional description
- —The hardcoded card ID '43' in the path suggests this may be a specific resource rather than a general-purpose endpoint
Citations
- —The endpoint returns a 402 x402 challenge with maxAmountRequired of 20000 base units in USDC on Base networkhttps://lowpaymentfee.com/api/v1/cards/43/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 contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/cards/43/transactions
- —Documentation pages (/docs, /api, /pricing, /README) render only a 'Connect wallet' prompthttps://lowpaymentfee.com/docs