x402-gated card transactions endpoint on Base, pay $0.02 per request in USDC.
What it does
This endpoint at lowpaymentfee.com provides access to a card transactions resource at `/api/v1/cards/4/transactions` via the x402 payment protocol. The endpoint is live and returns a standard 402 challenge requiring payment of up to 20,000 base units of USDC (0x8335…) on the Base network, which equals $0.02 per request (USDC uses 6 decimals). 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.
The broader lowpaymentfee.com platform advertises a wide catalog of x402-gated 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 uniformly at $0.02 per request. However, this specific listing covers only the `/api/v1/cards/4/transactions` endpoint, which appears to be a card-related transactions resource. The exact request body schema and response format are not documented in the crawled material; the endpoint accepts HTTP POST and returns `application/json`.
Documentation on the site 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 examples, and no detailed description of what "card transactions" means in this context. Prospective callers should be aware that the actual functionality behind this endpoint is unclear from available sources.
Capabilities
Use cases
- —Retrieving or submitting card transaction data via a pay-per-request model
- —Integrating card transaction lookups into agent workflows without API key management
- —Testing x402 payment protocol integrations on Base network
Fit
Best for
- —Developers experimenting with x402 protocol payments on Base
- —Agents needing keyless, pay-per-call access to card transaction data
- —Projects that want to avoid subscription commitments for occasional API calls
Not for
- —Production use cases requiring well-documented request/response schemas
- —High-volume batch processing where per-request pricing is inefficient
- —Users who need fiat-only payment rails (this requires USDC on Base)
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/cards/4/transactions \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>" \
-d '{}'Endpoint
Quality
The endpoint is live (402 challenge confirmed) and pricing is clear ($0.02 USDC on Base), but there is no documentation, no OpenAPI spec, no request/response examples, and no explanation of what the card transactions endpoint actually does. 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 schema describing request body or response format for this endpoint
- —The purpose of '/api/v1/cards/4/transactions' is unclear — 'Premium API Access' is a generic label
- —No request or response examples available from any source
Citations
- —Endpoint returns 402 with x402 challenge requiring up to 20,000 base units of USDC on Base networkhttps://lowpaymentfee.com/api/v1/cards/4/transactions
- —USDC asset address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/cards/4/transactions
- —Platform advertises $0.02 per request with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —Docs, API, pricing, and README pages render only 'Connect wallet' with no further contenthttps://lowpaymentfee.com/docs