# Forge Cascade Agent Payments – x402 Payment Challenge

> Forge Cascade Agent Payments – x402 Payment Challenge is a paid API for AI agents from api.relai.fi, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-13).

Issues an x402 Payment Required challenge to discovery clients, enabling micropayment-gated API access via the x402 protocol.

## Facts

- Endpoint: POST https://api.relai.fi/relay/1781295889777/api?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/forge-cascade-agent-payments-x402-payment-challenge-2219ce42
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_VlgTu5mm6il4Wu_bZ6N7x

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 forge-cascade-agent-payments-x402-payment-challenge-2219ce42 -d '<json body>'
```

Example prompt: Send a payment challenge probe to the Forge Cascade Agent Payments endpoint so I can discover the x402 payment terms and USDC price required before proceeding with the call.

## When to prefer this

Use this endpoint when you need to discover or initiate the x402 micropayment challenge flow for an API gated behind payment, specifically in agentic or automated contexts where the AI agent must negotiate payment terms before proceeding. Ideal for probing relay-hosted APIs on relai.fi that require USDC micropayments.

## Known failure modes

- Malformed request body returns 400 Bad Request
- Network timeout if relay is unavailable
- Unexpected 200 instead of 402 if payment gating is misconfigured
- Payment token already consumed returns 402 with different challenge
- Client does not support x402 protocol, cannot parse challenge

## How this service works

Returns an x402 Payment Required challenge for discovery clients.

## Output

Returns an HTTP 402 Payment Required response containing an x402 challenge payload specifying the payment amount (0.01 USDC), accepted payment method, and instructions needed for a client to construct and submit a valid payment to gain access.

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/forge-cascade-agent-payments-x402-payment-challenge-2219ce42/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)