x402-gated premium API endpoint on Base, pay-per-request with USDC.
What it does
This endpoint at `/api/v1/portfolios/77` is part of the lowpaymentfee.com platform, which offers a collection of x402-protocol pay-per-call APIs spanning data analytics, AI/ML inference, finance/Web3, and infrastructure utilities. The specific `/portfolios/77` resource is listed under "Premium API Access" but its exact functionality is not documented in the available crawl material — it does not appear on the site's main API listing page, which focuses on analytics, AI, finance, and utility endpoints.
The endpoint is live and returns a valid x402 challenge. Payment is settled on the Base network using USDC (contract `0x8335...2913`). The `maxAmountRequired` is 20,000 base units, which at 6 decimals equals $0.02 per request — consistent with the platform's uniform $0.02/request pricing. The platform advertises no API keys, no rate limits, and instant access; callers simply attach an x402 payment header to each POST request.
Because the `/portfolios/77` endpoint is not described on the landing page or in any crawled documentation, its input schema and response format are unknown. The docs, pricing, and README pages all returned only a "Connect wallet" prompt with no substantive content. Treat this as a stub listing until the provider publishes documentation for this specific resource.
Capabilities
Use cases
- —Accessing a premium portfolio data resource via a single micropayment
- —Integrating pay-per-request API calls into agent workflows without API keys
- —Settling API access costs on-chain via USDC on Base
Fit
Best for
- —Developers wanting keyless, pay-per-call API access
- —Agent systems that can handle x402 payment challenges natively
- —Users who prefer on-chain USDC micropayments over subscriptions
Not for
- —Users needing detailed documentation or guaranteed SLAs before integrating
- —High-volume batch consumers who need bulk pricing or rate-limit guarantees
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/portfolios/77 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>"Endpoint
Quality
The endpoint is live and returns a valid x402 challenge, but the specific /portfolios/77 resource has no documentation, no input/output schema, and does not appear on the provider's own API listing. Docs pages returned only 'Connect wallet' with no content. This is effectively a stub.
Warnings
- —The /api/v1/portfolios/77 endpoint is not listed on the provider's main API catalog page — its purpose is unclear.
- —All documentation pages (docs, pricing, README, api) returned only a 'Connect wallet' prompt with no substantive content.
- —No input or output schema is available for this endpoint; request format must be guessed or discovered experimentally.
- —The provider site lists many endpoints but none under a 'portfolios' category — this may be a test or unlisted resource.
Citations
- —The endpoint returns a valid x402 challenge with maxAmountRequired of 20000 base units on Base network using USDChttps://lowpaymentfee.com/api/v1/portfolios/77
- —The platform charges $0.02 per request with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/portfolios/77