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 the x402 payment protocol. The specific resource `/api/v1/portfolios/18/transactions` accepts POST requests and charges up to $0.02 per call in USDC on the Base network. Payment is handled entirely through the x402 challenge-response flow — no API keys or accounts are required.
The parent site lowpaymentfee.com hosts a broad catalog of x402-gated APIs spanning data analytics, AI/ML inference, finance/Web3 data, and infrastructure utilities, all priced at $0.02 per request. However, this particular endpoint appears to serve portfolio-level transaction data (portfolio ID 18). No OpenAPI schema, request body documentation, or response examples are available from the crawled material, so the exact input parameters and output format remain unknown. The docs, pricing, and API pages behind the site all resolve to a minimal "Connect wallet" prompt with no further detail.
Settlement occurs on Base mainnet to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` using USDC (`0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`). The x402 challenge specifies `maxAmountRequired` of 20000 base units, which at 6 decimals equals $0.02. The timeout for payment is 300 seconds.
Capabilities
Use cases
- —Fetching transaction history for a specific portfolio
- —Integrating portfolio transaction data into dashboards or analytics pipelines
- —Agent-driven portfolio monitoring with per-call payment
Fit
Best for
- —Developers wanting keyless, pay-per-call access to portfolio transaction data
- —AI agents that can settle x402 payments on Base
- —Users who prefer crypto micropayments over subscription billing
Not for
- —Users needing detailed API documentation or guaranteed SLAs before integrating
- —Applications requiring non-crypto payment methods
- —Bulk historical data exports where per-call pricing would be expensive
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/portfolios/18/transactions \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is live and returns a valid x402 challenge, confirming pricing and settlement details. However, there is no OpenAPI schema, no request/response documentation, and the crawled docs pages are empty stubs. The purpose of this specific endpoint (portfolio 18 transactions) is only inferable from the URL path. Effectively a stub listing.
Warnings
- —No API documentation available — docs, pricing, and API pages all show only a 'Connect wallet' prompt with no content.
- —No request body schema or response schema documented; input/output format is unknown.
- —The endpoint targets a hardcoded portfolio ID (18); unclear if this is a demo or production resource.
- —The broader site advertises many API categories but none have visible documentation.
Citations
- —The endpoint returns a 402 x402 challenge with maxAmountRequired of 20000 base units in USDC on Basehttps://lowpaymentfee.com/api/v1/portfolios/18/transactions
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/portfolios/18/transactions
- —Site advertises $0.02 per request, no API keys, no rate limits, instant access on Base networkhttps://lowpaymentfee.com
- —Payment timeout is 300 secondshttps://lowpaymentfee.com/api/v1/portfolios/18/transactions