x402-gated portfolio transactions endpoint on Base, pay-per-call with USDC.
What it does
This endpoint at lowpaymentfee.com exposes a POST-based portfolio transactions API at `/api/v1/portfolios/15/transactions`, gated by the x402 payment protocol. Each call costs up to $0.02 USDC (maxAmountRequired of 20,000 base units with 6 decimals) settled on the Base network. No API keys or rate limits are required — callers simply attach an X-PAYMENT header with a valid x402 payment proof.
The endpoint is part of a broader platform (lowpaymentfee.com) that offers dozens of pay-per-request APIs spanning data analytics, AI/ML inference, finance/Web3 data, and utility services, all priced at $0.02 per request. However, the specific `/portfolios/15/transactions` path is not listed on the site's public catalog, and no documentation describes its request or response schema. The "Premium API Access" label is the only description provided by the x402 challenge.
Because there is no OpenAPI spec, no request/response schema documentation, and the crawled docs/pricing/API pages all returned only a "Connect wallet" stub, the actual functionality of this particular endpoint is unclear. It likely involves creating or retrieving transactions for a specific portfolio (ID 15), but the exact input fields and output format are unknown. Callers should treat this as an exploratory endpoint until more documentation surfaces.
Capabilities
Use cases
- —Submitting or retrieving transactions for a portfolio via a pay-per-call model
- —Programmatic portfolio management without API key registration
- —Agent-driven financial transaction recording with instant USDC settlement
Fit
Best for
- —Developers wanting keyless, pay-per-use portfolio transaction access
- —AI agents that can settle x402 payments on Base
- —Users who prefer crypto micropayments over subscription billing
Not for
- —Anyone needing documented request/response schemas before integrating
- —High-volume batch transaction processing where per-call fees add up
- —Users without USDC on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/portfolios/15/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 zero documentation on request/response schema, no OpenAPI spec, and the crawled pages are mostly empty stubs. The specific portfolio transactions path is not even listed in the site's own catalog, making this effectively a stub listing.
Warnings
- —No request or response schema documented — callers must guess at the POST body format
- —This specific endpoint (/api/v1/portfolios/15/transactions) is not listed in the site's public API catalog
- —All documentation pages (docs, api, pricing, README) returned only a 'Connect wallet' stub with no useful content
- —The hardcoded portfolio ID '15' in the path suggests this may be a demo or single-tenant endpoint
Citations
- —The x402 challenge returns maxAmountRequired of 20000 base units in USDC (USD Coin) on the Base networkhttps://lowpaymentfee.com/api/v1/portfolios/15/transactions
- —The site advertises $0.02 per request pricing with no API keys, no rate limits, and instant access on the Base networkhttps://lowpaymentfee.com
- —The USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/portfolios/15/transactions