# Agoreum Payment Feedback Builder

> Agoreum Payment Feedback Builder is a paid API for AI agents from agoreum.xyz, paid per call via x402, $0.5/call, status unknown (last checked 2026-10-16).

Verifies an on-chain USDC payment transaction and constructs an ERC-8004 feedback file with that payment as cryptographic proof, ready for wallet submission.

## Facts

- Endpoint: POST https://agoreum.xyz/api/v1/x402/tools/payment-feedback?utm_source=zero.xyz
- Price: $0.5/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-16
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agoreum-payment-feedback-builder-c418ff47
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_gATieK8KXtcar2iiYgxtR

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 agoreum-payment-feedback-builder-c418ff47 -d '<json body>'
```

Example prompt: I just paid agent ID 42 on the /api/v1/summarize endpoint with tx hash 0x3a1b2c...f9 — can you verify the payment on-chain and build the ERC-8004 feedback file with a rating of 85 and a comment saying 'Fast and accurate responses'?

## When to prefer this

Use this endpoint when you need to create ERC-8004 feedback records that are cryptographically backed by an on-chain USDC payment — specifically in x402-based agent payment flows where proof-of-payment is required before feedback is considered legitimate. Prefer this over generic feedback or rating systems when you need trustless, wallet-submittable attestations tied to real transactions.

## Known failure modes

- Transaction hash not found on-chain — returns error if the tx_hash does not resolve to a valid USDC payment
- Payment amount insufficient — returns error if the on-chain payment does not meet the required threshold
- Invalid tx_hash format — rejected if the hash does not match the 0x + 64 hex character pattern
- Agent ID not recognized — error if agent_id does not correspond to a known agent
- Rating out of range — rejected if value is outside 0–100
- Comment too long — rejected if comment exceeds 1000 characters
- Endpoint string too long — rejected if endpoint exceeds 512 characters

## How this service works

Checks on chain that you paid an agent in USDC, then builds the ERC-8004 feedback file with that payment as proof, ready for your wallet to send.

## Output

An ERC-8004 compliant feedback file containing the verified payment transaction as proof of service, including the rating score, comment, agent ID, and endpoint reference — structured and ready for the caller's wallet to broadcast or submit on-chain.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "value": {
   "type": "integer",
   "maximum": 100,
   "minimum": 0
  },
  "comment": {
   "type": "string",
   "maxLength": 1000
  },
  "tx_hash": {
   "type": "string",
   "pattern": "^0x[0-9a-fA-F]{64}$"
  },
  "agent_id": {
   "type": "integer",
   "minimum": 0
  },
  "endpoint": {
   "type": "string",
   "maxLength": 512
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agoreum-payment-feedback-builder-c418ff47/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agoreum.xyz](https://www.zero.xyz/host/agoreum.xyz/llms.txt)