x402-gated portfolio transactions endpoint on Base, paid per-call in USDC.
What it does
This endpoint at lowpaymentfee.com exposes a POST-based API for portfolio transactions at `/api/v1/portfolios/94/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 payable per-request in USDC on the Base network with no API keys or rate limits required.
The specific endpoint probed here returns an x402 challenge requesting up to 20,000 base units of USDC (0x8335…2913 on Base). Since USDC uses 6 decimals, this translates to $0.02 per request, consistent with the site's advertised flat pricing of $0.02/request across all endpoints. Payment is settled on-chain via the x402 "exact" scheme to the payTo address 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3, with a maximum timeout of 300 seconds.
Documentation is extremely sparse — the docs, pricing, and API pages all render only a "Connect wallet" prompt with no further content. There is no OpenAPI spec, no request/response schema documentation, and no explanation of what the `/portfolios/94/transactions` endpoint actually returns or what input it expects. The endpoint is live (402 challenge confirmed), but without documentation it is unclear what data or functionality is provided. The platform appears to be a demonstration or early-stage x402 API marketplace.
Capabilities
Use cases
- —Submitting or retrieving portfolio transaction data via a pay-per-call model
- —Integrating x402 payment flows into agent-based workflows
- —Testing x402 protocol implementations against a live endpoint
Fit
Best for
- —Developers experimenting with x402 payment protocol on Base
- —Agents that need to make on-chain micropayments for API access
- —Projects exploring keyless, pay-per-request API consumption
Not for
- —Production use cases requiring documented request/response schemas
- —Users who need free or subscription-based API access
- —Applications requiring high-throughput with predictable latency guarantees
Quick start
# 1. Send a POST to get the x402 payment challenge
curl -X POST https://lowpaymentfee.com/api/v1/portfolios/94/transactions
# Returns 402 with x402 challenge in response body
# 2. Construct X-PAYMENT header with USDC payment proof on Base
# 3. Resend POST with X-PAYMENT header to access the resourceExample
Response
{
"error": "X-PAYMENT header is required",
"accepts": [
{
"asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
"extra": {
"name": "USD Coin",
"version": "2"
},
"payTo": "0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3",
"scheme": "exact",
"network": "base",
"mimeType": "application/json",
"resource": "https://lowpaymentfee.com/api/v1/portfolios/94/transactions",
"description": "Premium API Access",
"maxAmountRequired": "20000",
"maxTimeoutSeconds": 300
}
],
"x402Version": 1
}Endpoint
Quality
The endpoint is live and returns a valid x402 challenge with clear pricing ($0.02 USDC on Base). However, there is no documentation, no OpenAPI spec, no request/response schema, and no explanation of what the endpoint actually does beyond the generic label 'Premium API Access'. The docs pages are empty. This is effectively a stub listing.
Warnings
- —No documentation available — docs, pricing, and API pages all render only 'Connect wallet' with no content
- —No OpenAPI or request/response schema provided; unclear what input the POST endpoint expects
- —The endpoint path references a specific portfolio ID (94) with no explanation of what portfolios are available or how IDs are assigned
- —Platform appears to be early-stage or a demonstration; reliability and longevity are unknown
Citations
- —The endpoint returns an x402 challenge with maxAmountRequired of 20000 base units of USDC on Base networkhttps://lowpaymentfee.com/api/v1/portfolios/94/transactions
- —The platform advertises $0.02/request flat pricing with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —USDC contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/portfolios/94/transactions
- —Docs, pricing, and API pages render only a 'Connect wallet' prompt with no further contenthttps://lowpaymentfee.com/docs