# Rubric Protocol C2PA Verdict Attestation (Tier B)

> Rubric Protocol C2PA Verdict Attestation (Tier B) is a paid API for AI agents from rubric-protocol.com, paid per call via x402, $0.05/call, status unknown (last checked 2026-09-14).

Attests a C2PA content authenticity verdict by accepting a verdict JSON, asset hash, and client signature produced by a locally-run Credentio instance, returning a signed attestation claim.

## Facts

- Endpoint: POST https://rubric-protocol.com/v1/c2pa/verdict-attest/claim
- Price: $0.05/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/rubric-protocol-c2pa-verdict-attestation-tier-b-955002ab
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_nxTw9zb-8_VkEZw5Vjeyf

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 rubric-protocol-c2pa-verdict-attestation-tier-b-955002ab -d '<json body>'
```

Example prompt: I ran Credentio locally on this image and have the verdict JSON, asset hash, and my client signature ready — can you submit them to Rubric Protocol's Tier B C2PA attestation endpoint to get a signed claim back?

## When to prefer this

Choose this endpoint when you have already run Credentio locally and need to elevate a local C2PA verdict to a third-party attested claim with cryptographic anchoring. Tier B is appropriate when full Tier A on-chain immutability is not required but a signed, verifiable attestation from Rubric Protocol is needed for compliance, publication, or audit trails. Prefer this over self-signed solutions when downstream consumers require an independent attestation authority.

## Known failure modes

- Invalid or missing client signature — returns 400/422 with signature validation error
- Asset hash mismatch or tampered verdict JSON — attestation rejected
- Malformed verdict JSON structure — returns schema validation error
- Insufficient USDC balance / x402 payment failure — returns 402 Payment Required
- Rate limiting or service unavailability — returns 429 or 503

## How this service works

C2PA verdict attestation Tier B. Client runs Credentio locally, submits verdict JSON + asset hash + client signature. Ru

## Output

A signed C2PA attestation claim (verdict receipt) anchored by Rubric Protocol, confirming the submitted verdict JSON, asset hash, and client signature were accepted and attested at Tier B. This can be embedded in the asset's content credentials or stored for audit purposes.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "object"
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json"
     ],
     "type": "string"
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "format": {
     "type": "string"
    },
    "example": {}
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/rubric-protocol-c2pa-verdict-attestation-tier-b-955002ab/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from rubric-protocol.com](https://www.zero.xyz/host/rubric-protocol.com/llms.txt)