x402-gated card-transaction 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/32/transactions` behind the x402 payment protocol. When called without payment, it returns a 402 challenge requesting USDC on the Base network. The maximum amount required per call is 20,000 base units of USDC (6 decimals), which equals $0.02 per request. Payment is sent to the specified wallet address and settled on-chain.
The hosting site lowpaymentfee.com advertises a broad catalog of pay-per-request APIs spanning data & analytics, AI/ML inference (sentiment analysis, summarization, classification, embeddings), finance & Web3 (price feeds, exchange rates, token quotes, gas estimates), and infrastructure utilities (geocoding, validation, conversion, generation). All endpoints are listed at $0.02 per request with no API keys, no rate limits, and no minimum commitments. However, the specific endpoint being listed here — `/api/v1/cards/32/transactions` — is labeled "Premium API Access" and does not appear in the site's public catalog, so its exact functionality is unclear.
The endpoint accepts HTTP POST requests and returns `application/json`. No OpenAPI schema, request body documentation, or response examples were found in the crawled material. The docs, pricing, and API pages all rendered only a "Connect wallet" prompt with no additional content. Because the actual purpose of this particular cards/transactions resource is undocumented, agents should treat this listing with caution until more documentation surfaces.
Capabilities
Use cases
- —Submitting or retrieving card transaction data via a pay-per-call model
- —Integrating x402-compatible payment flows into agent workflows
- —Testing x402 protocol implementations against a live endpoint
Fit
Best for
- —Developers experimenting with x402 payment protocol on Base
- —Agents that can settle USDC micropayments on Base L2
- —Use cases needing keyless, per-request API access
Not for
- —Users who need detailed API documentation before integrating
- —High-volume batch processing where $0.02/request adds up quickly
- —Anyone needing non-crypto payment options
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/cards/32/transactions
# Returns 402 with x402 challenge; include X-PAYMENT header with valid USDC payment proof to access.Example
Response
{
"error": "X-PAYMENT header is required",
"accepts": [
{
"asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
"payTo": "0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3",
"scheme": "exact",
"network": "base",
"mimeType": "application/json",
"description": "Premium API Access",
"maxAmountRequired": "20000"
}
],
"x402Version": 1
}Endpoint
Quality
The endpoint is live and returns a valid x402 challenge, but there is no documentation for the specific /cards/32/transactions resource — no request schema, no response examples, and no explanation of what it does. The site's docs pages are empty. The endpoint doesn't appear in the site's own public catalog, making its purpose unclear.
Warnings
- —The specific endpoint /api/v1/cards/32/transactions is not listed in the site's public API catalog and its function is undocumented.
- —All documentation pages (docs, pricing, API, README) render only a 'Connect wallet' prompt with no usable content.
- —No request body schema or response schema is available; agents cannot know what to POST.
- —The site lists many diverse API categories (AI, finance, geo, etc.) all at $0.02 — it is unclear whether these are fully functional or placeholder endpoints.
Citations
- —The endpoint returns a 402 challenge requesting 20,000 base units of USDC on Base networkhttps://lowpaymentfee.com/api/v1/cards/32/transactions
- —The site advertises $0.02/request pricing with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/cards/32/transactions
- —Docs, pricing, API, and README pages show only 'Connect wallet' with no additional contenthttps://lowpaymentfee.com/docs