x402-gated portfolio endpoint on Base, pay $0.02 per request in USDC — no API keys required.
What it does
This endpoint at lowpaymentfee.com provides access to a specific portfolio resource (ID 73) via the x402 payment protocol. It is part of a broader platform that offers a variety of pay-per-call APIs spanning data analytics, AI/ML inference, finance/Web3 data, and infrastructure utilities — all gated behind x402 micropayments on the Base network using USDC.
The endpoint accepts POST requests and returns JSON. Payment is settled on-chain via USDC on Base (contract 0x8335…2913) using the "exact" x402 scheme. The x402 challenge advertises a maxAmountRequired of 20,000 base units; since USDC uses 6 decimals, this equals $0.02 per request, consistent with the site's advertised flat pricing. No API keys, rate limits, or upfront commitments are required — callers simply attach an X-PAYMENT header with a valid x402 payment proof.
The specific data returned by the /api/v1/portfolios/73 endpoint is not documented in the crawled material. The site's landing page groups its APIs into categories (Data & Analytics, AI & ML, Finance & Web3, Infrastructure) but does not list a "portfolios" category or describe the schema of portfolio responses. As a result, the exact payload structure and use case for this particular endpoint must be inferred or discovered by making a paid call. The broader platform appears to be a demonstration or marketplace of low-fee x402 endpoints.
Capabilities
Use cases
- —Fetching portfolio data on-demand with per-request USDC micropayments
- —Agent-driven data retrieval without pre-registration or API key management
- —Integrating x402-compatible payment flows into automated pipelines
- —Exploring x402 protocol mechanics with a low-cost live endpoint
Fit
Best for
- —Developers experimenting with x402 payment protocol on Base
- —AI agents that need keyless, pay-per-call API access
- —Applications requiring on-chain micropayment settlement for API usage
Not for
- —Users who need detailed, documented portfolio data schemas before purchasing
- —High-throughput use cases where $0.02/request adds up significantly
- —Anyone without a Base-compatible USDC wallet
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/portfolios/73 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>"Endpoint
Quality
The endpoint is live (402 challenge captured) and pricing is clear ($0.02 USDC on Base). However, there is no documentation for the /portfolios/73 resource — no request schema, no response schema, no description of what portfolio data is returned. The docs, pricing, and README pages all returned only 'Connect wallet' with no useful content.
Warnings
- —No documentation exists for the /api/v1/portfolios/73 endpoint — its response schema and purpose are unknown.
- —The site's docs, pricing, and README pages are empty (only show 'Connect wallet'), suggesting the platform may be early-stage or incomplete.
- —The 'portfolios' category is not listed among the site's advertised API groups, raising questions about whether this is a production endpoint.
Citations
- —The x402 challenge advertises maxAmountRequired of 20000 base units in USDC on Base networkhttps://lowpaymentfee.com/api/v1/portfolios/73
- —USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/portfolios/73
- —Platform advertises $0.02 per request flat pricing with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —The site lists API categories: Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructurehttps://lowpaymentfee.com