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/14/transactions`, gated behind 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 advertises multiple API categories including Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructure utilities, all priced at $0.02 per request. However, the specific endpoint being listed here (`/portfolios/14/transactions`) is not explicitly documented on the site's landing page among the advertised APIs. Its exact input schema and response format are unknown — the x402 challenge confirms it accepts POST requests with `application/json` content type, but no further documentation or OpenAPI spec was found.
The x402 challenge is live and well-formed, paying to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` using USDC (`0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`) on Base. The timeout is 300 seconds. Because the endpoint path references a specific portfolio ID (14) and "transactions," it likely returns or creates transaction records for that portfolio, but this is inference only.
Capabilities
Use cases
- —Retrieving or creating transaction records for a specific portfolio
- —Programmatic portfolio management via pay-per-call access
- —Agent-driven financial data retrieval without API key provisioning
Fit
Best for
- —Agents needing keyless, pay-per-call access to portfolio transaction data
- —Developers experimenting with x402 payment protocol integrations
- —Automated workflows that need on-demand financial transaction endpoints
Not for
- —Users who need detailed API documentation or guaranteed schema stability
- —High-volume bulk data retrieval where per-call pricing is cost-prohibitive
- —Production systems requiring SLA guarantees or support
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/portfolios/14/transactions \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>" \
-d '{}'Endpoint
Quality
The x402 challenge is live and well-formed, confirming the endpoint exists and accepts payments. However, there is no OpenAPI spec, no documented request/response schema, no examples, and the specific endpoint path (/portfolios/14/transactions) is not listed among the site's advertised APIs. The crawled docs/pricing/README pages returned only 'Connect wallet' with no useful content.
Warnings
- —The endpoint /api/v1/portfolios/14/transactions is not listed among the site's advertised APIs — its purpose and schema are unknown.
- —No OpenAPI spec, request schema, or response examples are available.
- —Documentation pages (/docs, /pricing, /README, /api) returned no meaningful content beyond 'Connect wallet'.
- —The hardcoded portfolio ID '14' in the path suggests this may be a specific resource rather than a general-purpose API.
Citations
- —The x402 challenge returns maxAmountRequired of 20000 base units in USDC on Base networkhttps://lowpaymentfee.com/api/v1/portfolios/14/transactions
- —USDC contract address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/portfolios/14/transactions
- —The site advertises $0.02 per request pricing with no API keys, no rate limitshttps://lowpaymentfee.com
- —The site lists APIs across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com