x402-gated card-transaction endpoint on Base, paying $0.02 per request in USDC.
What it does
This endpoint at lowpaymentfee.com exposes a card-transactions resource at `/api/v1/cards/16/transactions` behind an x402 payment challenge. It is part of a broader platform (lowpaymentfee.com) that offers dozens of pay-per-call APIs spanning data analytics, AI/ML inference, finance/Web3 data, and infrastructure utilities — all gated via the x402 protocol on the Base network.
The specific endpoint accepts POST requests and requires an X-PAYMENT header carrying an x402 payment proof. The challenge advertises a maximum amount of 20,000 base units of USDC (contract 0x8335…2913 on Base), which at 6 decimals equals $0.02 per request. Payment is settled on-chain to address 0x1A2B…85F3. The platform advertises no API keys, no rate limits, and instant access — you pay per call and that's it.
Documentation is extremely thin: 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, and no usage examples available from the crawl. The endpoint's purpose — retrieving or creating transactions for "card 16" — is not explained anywhere in the crawled material. Without documentation it is unclear what request body fields are expected or what the response looks like.
Capabilities
Use cases
- —Querying or creating card transaction records via a pay-per-call model
- —Integrating card transaction data into agent workflows without API key management
- —Demonstrating x402 protocol payment flows on Base
Fit
Best for
- —Developers experimenting with x402 payment-gated APIs
- —Agents that need keyless, pay-per-request access to card transaction data
- —Projects already operating on the Base L2 with USDC
Not for
- —Production use cases requiring documented request/response schemas
- —Users who need free or subscription-based access without per-call crypto payments
- —Anyone needing detailed card transaction analytics with well-documented fields
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/cards/16/transactions \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>"Endpoint
Quality
The endpoint is live (402 challenge confirmed) and pricing is clear ($0.02 USDC on Base), but there is zero documentation on request/response schemas, no OpenAPI spec, and the docs pages are empty. The purpose of 'cards/16/transactions' is unexplained. This is effectively a stub listing.
Warnings
- —No documentation available — docs, API, pricing, and README pages all show only 'Connect wallet' with no content.
- —No OpenAPI or request/response schema provided; request body format is unknown.
- —The specific purpose of /api/v1/cards/16/transactions is not documented anywhere in crawled material.
- —This endpoint path references a hardcoded resource ID (card 16) with no explanation of what it represents.
Citations
- —The endpoint returns a 402 challenge with maxAmountRequired of 20000 base units of USDC on Base network.https://lowpaymentfee.com/api/v1/cards/16/transactions
- —The platform advertises $0.02 per request, no API keys, no rate limits, and instant access on Base network.https://lowpaymentfee.com
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913.https://lowpaymentfee.com/api/v1/cards/16/transactions