# LiquProp API - Get Sign-In Nonce

> LiquProp API - Get Sign-In Nonce is a paid API for AI agents from api.relai.fi, paid per call via x402, $0.01/call, status down (last checked 2026-09-15).

Returns a one-time nonce for wallet-based authentication (Sign-In with Ethereum / SIWE) for a given wallet address

## Facts

- Endpoint: POST https://api.relai.fi/relay/1776502063891/v1/auth/nonce/{address}
- Price: $0.01/call
- Payment: x402
- Status: down
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/liquprop-api-7f1e3296
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap__K0oqePAf2kFeUwLVU7EN

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability liquprop-api-7f1e3296 -d '<json body>'
```

Example prompt: I need to start the sign-in flow for my wallet address 0x1234abcd5678ef90... — can you get a nonce from LiquProp so I can sign it and complete authentication?

## When to prefer this

Use this endpoint when implementing wallet-based authentication (SIWE / Sign-In with Ethereum) for the LiquProp platform. Choose this over generic auth endpoints when the user needs to authenticate a specific Ethereum/Polygon wallet address and you need a server-generated nonce to prevent replay attacks.

## Known failure modes

- Invalid or malformed wallet address returns error
- Address not found or not registered may return 404
- Network timeout or relay unavailability returns 5xx
- Expired session or repeated nonce request may be rejected
- Payment of 0.01 USDC not fulfilled returns 402

## How this service works

Get a sign-in nonce for a wallet address

## Output

A one-time nonce value that the wallet owner must sign to prove ownership of the address, completing the Sign-In with Ethereum (SIWE) authentication challenge.

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/liquprop-api-7f1e3296/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.relai.fi](https://www.zero.xyz/host/api.relai.fi/llms.txt)