x402-gated portfolio transactions endpoint on Base, pay-per-call with USDC.
What it does
This endpoint at lowpaymentfee.com provides access to portfolio transaction data via a POST request to `/api/v1/portfolios/40/transactions`. It is part of a broader platform (lowpaymentfee.com) that offers a variety of pay-per-request APIs spanning data analytics, AI/ML inference, finance/Web3 data, and utility services — all gated behind the x402 payment protocol on the Base network.
The specific endpoint probed here returns an x402 challenge requesting payment in USDC (contract `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913` on Base). The `maxAmountRequired` is 20,000 base units, which at 6 decimals for USDC equals $0.02 per request. Payment is made via the x402 `exact` scheme, with a 300-second timeout. No API keys or rate limits are advertised; access is granted purely through per-call micropayment.
Documentation on the site is extremely sparse — the docs, pricing, API, and README pages all render only a "Connect wallet" prompt with no substantive content. There is no OpenAPI schema, no request/response examples, and no description of what fields the transactions endpoint accepts or returns. The endpoint name suggests it retrieves or creates transactions for a specific portfolio (ID 40), but the exact semantics, required POST body, and response format are unknown. The platform's landing page lists many other endpoints at $0.02 each across categories like sentiment analysis, text summarization, geocoding, and crypto gas estimates, but none have documented schemas either.
Capabilities
Use cases
- —Retrieving or posting portfolio transaction records via micropayment
- —Integrating pay-per-call financial data into agent workflows
- —Accessing portfolio data without API key registration
Fit
Best for
- —Agents or developers who want keyless, pay-per-request access to portfolio transaction data
- —x402-compatible clients on the Base network
- —Low-volume or exploratory use where per-call pricing is preferred over subscriptions
Not for
- —Users who need well-documented API schemas and response formats before integrating
- —High-volume consumers who would benefit from bulk pricing or subscriptions
- —Anyone requiring non-USDC or non-Base-network payment options
Quick start
# x402 endpoint — send a POST with X-PAYMENT header containing a valid x402 payment proof
curl -X POST https://lowpaymentfee.com/api/v1/portfolios/40/transactions \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402_payment_token>"Endpoint
Quality
The endpoint is live and returns a valid x402 challenge with clear pricing ($0.02 USDC on Base). However, there is no OpenAPI schema, no request/response documentation, no examples, and the docs pages are empty. The purpose of this specific endpoint (portfolios/40/transactions) is unclear beyond the name. This is effectively a stub listing.
Warnings
- —No OpenAPI schema or request/response documentation available
- —Docs, pricing, API, and README pages all render only 'Connect wallet' with no content
- —The specific purpose and accepted POST body for /api/v1/portfolios/40/transactions is undocumented
- —Portfolio ID 40 is hardcoded in the URL — unclear if other portfolio IDs are available or what this portfolio represents
- —The broader platform lists many endpoints but none appear to have documented schemas
Citations
- —The endpoint returns an x402 challenge with maxAmountRequired of 20000 base units in USDC on Base networkhttps://lowpaymentfee.com/api/v1/portfolios/40/transactions
- —USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/portfolios/40/transactions
- —Platform advertises $0.02 per request, no API keys, no rate limits, instant access on Base networkhttps://lowpaymentfee.com
- —Docs, pricing, API, and README pages render only 'Connect wallet' with no documentation contenthttps://lowpaymentfee.com/docs