x402-gated portfolio transactions endpoint on Base, pay $0.02 per request in USDC.
What it does
This endpoint at lowpaymentfee.com provides access to portfolio transaction data via a POST request to `/api/v1/portfolios/4/transactions`. It is part of a broader platform (lowpaymentfee.com) that offers dozens of x402-gated API endpoints spanning data analytics, AI/ML inference, finance/Web3 data, and infrastructure utilities — all priced at $0.02 per request.
Payment is handled via the x402 protocol on the Base network using USDC (contract `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`). The max amount required is 20,000 base units of USDC (6 decimals), which equals $0.02. No API keys are needed; callers simply attach an `X-PAYMENT` header with a valid x402 payment proof. The platform advertises no rate limits and instant access.
The specific functionality of this particular endpoint — portfolio transactions for portfolio ID 4 — is not well-documented. The landing page does not list this endpoint among its advertised APIs, and the docs, pricing, and API pages all render only a "Connect wallet" prompt with no additional content. It is unclear what request body this POST endpoint expects or what transaction data it returns. The endpoint is confirmed live (returns a proper 402 challenge), but the lack of documentation on input/output schemas limits its usability without further experimentation.
Capabilities
Use cases
- —Fetching portfolio transaction history via a single paid API call
- —Integrating pay-per-request financial data into agent workflows
- —Accessing transaction data without managing API keys or subscriptions
Fit
Best for
- —Agents or developers who want keyless, pay-per-call access to portfolio data
- —Crypto-native applications already on the Base network
- —Prototyping integrations without upfront API key registration
Not for
- —Users who need detailed API documentation and schemas before integrating
- —High-volume consumers who would prefer subscription-based pricing
- —Anyone needing portfolio IDs other than 4 (no evidence of parameterized access)
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/portfolios/4/transactions \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>"Endpoint
Quality
The endpoint is confirmed live with a valid x402 402 challenge, but there is no documentation on request/response schemas, no OpenAPI spec, and the specific endpoint is not listed among the platform's advertised APIs. Docs pages are empty beyond a wallet connect prompt. Effectively a stub with confirmed liveness.
Warnings
- —This specific endpoint (/api/v1/portfolios/4/transactions) is not listed among the platform's advertised APIs — its purpose and expected input/output are undocumented.
- —All documentation pages (docs, pricing, API, README) render only a 'Connect wallet' prompt with no usable content.
- —No request body schema or response schema is available; callers must experiment to discover the expected format.
- —The hardcoded portfolio ID '4' in the URL suggests this may be a specific resource rather than a general-purpose endpoint.
Citations
- —The endpoint returns a 402 challenge with maxAmountRequired of 20000 base units of USDC on Base networkhttps://lowpaymentfee.com/api/v1/portfolios/4/transactions
- —The platform advertises $0.02 per request pricing with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/portfolios/4/transactions