# LiquProp API – Gas-Free Relay Payment

> LiquProp API – Gas-Free Relay Payment 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).

Submits a blockchain transaction on Polygon with RelAI sponsoring the gas fee, enabling gas-free payments via x402 protocol

## Facts

- Endpoint: POST https://api.relai.fi/relay/1776502063891/
- 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-9f54733e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Vt0POh2Zha5aNwyNYW2_d

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-9f54733e -d '<json body>'
```

Example prompt: Send a gas-free USDC payment on Polygon using RelAI's relay — I don't want to pay any gas fees myself, so have RelAI sponsor the transaction fees for a 0.01 USDC call.

## When to prefer this

Use this endpoint when you need to execute Polygon transactions without holding MATIC for gas, or when building applications where end-users should not be burdened with gas fee management. Ideal for x402-protocol payment flows where RelAI's gas sponsorship simplifies the UX.

## Known failure modes

- Insufficient USDC balance to cover the $0.01 per-call fee
- Invalid or malformed transaction payload returns 400 error
- Relay service temporarily unavailable returns 503
- Polygon network congestion causing delayed or failed relay
- x402 payment header missing or invalid returns 402

## How this service works

Gas-free payment - RelAI sponsors transaction fees on polygon

## Output

A relay confirmation response including the transaction hash and receipt indicating that RelAI successfully submitted and paid for the gas on the Polygon network on the caller's behalf.

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/liquprop-api-9f54733e/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)