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/54/transactions` accepts POST requests and charges up to $0.02 per call in USDC on the Base network. Payment is handled inline via the x402 header challenge — no API keys or accounts are required.
The broader lowpaymentfee.com platform advertises a range of pay-per-request APIs spanning data analytics, AI/ML inference (sentiment, summarization, classification, embeddings), finance/Web3 (price feeds, exchange rates, token quotes, gas estimates), and infrastructure utilities (geocoding, validation, conversion, generation), all at a uniform $0.02 per request. However, the specific endpoint listed here targets portfolio 54's transactions, which appears to be a finance-related resource. Documentation beyond the landing page is essentially empty (all sub-pages just show "Connect wallet"), so the exact request body schema, response format, and the nature of the portfolio data are unknown.
The endpoint is live and returns a valid x402 challenge (version 1) with USDC (contract 0x8335…2913) on Base. The payment scheme is "exact" with a max amount of 20000 base units (i.e., $0.02 given USDC's 6 decimals). Timeout is 300 seconds. No OpenAPI spec or detailed documentation is available, so integrators will need to experiment with the POST body to determine accepted parameters.
Capabilities
Use cases
- —Fetching transaction records for a specific portfolio via micropayment
- —Integrating pay-per-call financial data into an AI agent workflow
- —Accessing portfolio transaction data without API key registration
Fit
Best for
- —Agents needing on-demand portfolio transaction data with no signup
- —Developers experimenting with x402 payment protocol integrations
- —Micropayment-gated financial data access on Base
Not for
- —Users needing detailed API documentation or OpenAPI specs before integrating
- —Bulk historical transaction data retrieval (pay-per-call at $0.02 adds up)
- —Non-crypto-native users unfamiliar with x402 payment flows
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/portfolios/54/transactions \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402_payment_token>" \
-d '{}'Endpoint
Quality
The endpoint is live and returns a valid x402 challenge, but there is no documentation, no OpenAPI spec, no request/response schema, and no explanation of what portfolio 54 represents or what parameters the POST body accepts. All doc pages return only 'Connect wallet' with no content.
Warnings
- —No API documentation available — all doc/pricing/readme pages are empty stubs showing only 'Connect wallet'
- —Request body schema is completely unknown; no OpenAPI or example payloads provided
- —The specific portfolio ID (54) is hardcoded in the URL with no explanation of what it represents
- —Response format is undocumented — integrators must discover it experimentally
Citations
- —Endpoint returns a valid x402 challenge with USDC on Base, maxAmountRequired 20000 (=$0.02)https://lowpaymentfee.com/api/v1/portfolios/54/transactions
- —Platform advertises $0.02/request uniform pricing with no API keys, no rate limitshttps://lowpaymentfee.com
- —USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/portfolios/54/transactions