x402-gated card-transactions 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/14/transactions` behind the x402 payment protocol. It accepts HTTP 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 parent site lowpaymentfee.com hosts a broader catalog of pay-per-call APIs spanning data analytics, AI/ML inference (sentiment, summarization, classification, embeddings), finance/crypto market data, and utility services — all priced at $0.02 per request with no API keys, no rate limits, and no commitments. However, the specific `/api/v1/cards/14/transactions` endpoint is not listed on the site's public catalog, and no documentation, request schema, or response schema is available for it. The endpoint's purpose — whether it returns transaction history for a card, creates a transaction, or something else — cannot be confirmed from the available material.
The endpoint is live: it returns a well-formed x402 version-1 challenge with a 402 status code. Settlement is via the "exact" scheme on Base mainnet to address 0x1A2B…85F3, with a 300-second timeout. No OpenAPI spec, no usage examples, and no detailed docs were found.
Capabilities
Use cases
- —Retrieving or creating card transaction records via a pay-per-call model
- —Integrating card transaction data into agent workflows without API key management
- —Programmatic access to card-level transaction information settled in USDC on Base
Fit
Best for
- —Agents that can settle x402 USDC payments on Base
- —Use cases needing keyless, per-request API access to card transaction data
- —Developers exploring x402 protocol integrations
Not for
- —Users who need detailed API documentation or guaranteed SLAs before integrating
- —High-volume batch processing where $0.02/request adds up significantly
- —Anyone without a Base-compatible USDC wallet
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/cards/14/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 documentation, no request/response schema, and the specific endpoint is not listed on the provider's own catalog. The purpose and expected input/output of this particular resource are unknown.
Warnings
- —No OpenAPI spec or request/response schema available for this endpoint
- —The /api/v1/cards/14/transactions path is not listed on the provider's public API catalog — its function is unclear
- —Documentation pages (/docs, /api, /pricing, /README) returned only a 'Connect wallet' stub with no useful content
- —The endpoint's actual behavior (read vs. write, required body fields, response format) is entirely unknown
Citations
- —The x402 challenge advertises maxAmountRequired of 20000 base units of USDC on Base with a 300-second timeouthttps://lowpaymentfee.com/api/v1/cards/14/transactions
- —The site lists APIs at $0.02/request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —USDC asset address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/cards/14/transactions