# 8k4 Protocol — Create Signed Metadata Upload Nonce

> 8k4 Protocol — Create Signed Metadata Upload Nonce is a paid API for AI agents from api.8k4protocol.com, paid per call via x402, $0.001/call, status down (last checked 2026-09-15).

Generates a signed nonce required to authorize an ERC-8004 agent metadata upload

## Facts

- Endpoint: POST https://api.8k4protocol.com/metadata/nonce
- Price: $0.001/call
- Payment: x402
- Status: down
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/8k4-protocol-create-signed-metadata-upload-nonce-938155a7
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_T8YkxcGKvrsw9gIrLMd_J

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 8k4-protocol-create-signed-metadata-upload-nonce-938155a7 -d '<json body>'
```

Example prompt: I need to upload signed metadata for my ERC-8004 agent — can you get me a fresh signed upload nonce from the 8k4 Trust API so I can proceed with the metadata submission?

## When to prefer this

Use this endpoint as the mandatory first step before uploading signed ERC-8004 metadata. This nonce is required by the 8k4 Protocol's upload endpoint to ensure authenticity and prevent replay attacks. Choose this when your agent needs to publish or update its trust metadata on-chain via the 8k4 Protocol.

## Known failure modes

- Invalid or malformed properties payload returns a 400 error
- Missing required properties field causes schema validation failure
- Expired nonce if too much time passes before using it in the upload step
- Rate limiting or insufficient USDC balance causes payment failure via x402
- Network timeout or service unavailability returns 5xx error

## How this service works

Create a signed metadata upload nonce

## Output

A signed nonce value that must be included when calling the ERC-8004 metadata upload endpoint, serving as a one-time authorization token to prevent replay attacks and authenticate the upload request.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "properties": {
   "type": "string"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/8k4-protocol-create-signed-metadata-upload-nonce-938155a7/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.8k4protocol.com](https://www.zero.xyz/host/api.8k4protocol.com/llms.txt)