# Rubric Protocol – Attested Hedera USDC Supply

> Rubric Protocol – Attested Hedera USDC Supply is a paid API for AI agents from rubric-protocol.com, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-15).

Returns the current USDC circulating supply on the Hedera network, with a post-quantum ML-DSA-65 attestation ID proving the exact snapshot served.

## Facts

- Endpoint: GET https://rubric-protocol.com/v1/x402/hedera-facts/usdc-supply
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/rubric-protocol-attested-hedera-usdc-supply-fe0b01a1
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_U-7_aD6Q2Ha7yaEaL3S8Z

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-attested-hedera-usdc-supply-fe0b01a1
```

Example prompt: Pull the current attested USDC circulating supply on Hedera mainnet and give me the ML-DSA-65 attestation ID so I can log what the agent knew at the time of the decision.

## When to prefer this

Choose this endpoint when you need a cryptographically provable, post-quantum attested snapshot of USDC supply on Hedera — specifically when auditability, compliance, or tamper-evidence is required. Prefer over plain Hedera explorers or RPC calls when the agent must prove what data it acted upon at a specific moment.

## Known failure modes

- Payment not included or insufficient: 402 Payment Required
- Hedera network data temporarily unavailable: 503 Service Unavailable
- Malformed request: 400 Bad Request
- Attestation signing service offline: 503 with error detail
- Rate limiting on repeated requests: 429 Too Many Requests

## How this service works

Attested Hedera network facts: HBAR exchange rate, gas fees, supply, node roster, throughput, topic state. Each response

## Output

A JSON response containing the current USDC circulating supply on the Hedera network, along with an ML-DSA-65 post-quantum attestation ID that cryptographically binds the served value to a specific network snapshot, enabling tamper-evident auditing.

## 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"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "pathParams": {
     "type": "object",
     "required": [
      "fact"
     ],
     "properties": {
      "fact": {
       "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-attested-hedera-usdc-supply-fe0b01a1/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)