# Rubric Protocol – Attested Hedera HBAR Supply Facts

> Rubric Protocol – Attested Hedera HBAR Supply Facts is a paid API for AI agents from rubric-protocol.com, paid per call via x402, $0.004/call, status unknown (last checked 2026-09-15).

Returns cryptographically attested Hedera network supply metrics (HBAR circulating/total supply) anchored to Hedera HCS with a post-quantum signature.

## Facts

- Endpoint: POST https://rubric-protocol.com/v1/attested/https://rubric-protocol.com/v1/x402/hedera-facts/supply
- Price: $0.004/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-hbar-supply-facts-1effa076
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_D9rQnH4lxIpwa54xyFHEV

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-hbar-supply-facts-1effa076 -d '<json body>'
```

Example prompt: Can you fetch the current HBAR circulating and total supply from Hedera mainnet with a cryptographic attestation anchored to HCS, so I have a tamper-proof record I can use for our compliance report?

## When to prefer this

Choose this endpoint when you need cryptographically attested, independently verifiable Hedera HBAR supply data — not just a raw API response. It is ideal for compliance, audit, and DeFi use cases where tamper-evident proof of the supply figure (backed by post-quantum signatures and HCS anchoring) is required, rather than a plain REST call to a Hedera mirror node.

## Known failure modes

- Hedera mirror node unavailable — returns error indicating upstream data source failure
- Invalid or malformed POST body (missing required 'input' fields) — returns 400-level schema validation error
- Payment not completed or insufficient USDC — returns 402 Payment Required
- HCS anchoring delay — response may be slower than usual if Hedera network is congested
- Post-quantum signing service unavailable — attestation cannot be generated, returns 503

## How this service works

Rubric x402 service. Operated by Rubric Protocol.

## Output

Returns a structured JSON payload containing current HBAR supply metrics (circulating supply, total supply) along with a post-quantum cryptographic signature and a Hedera Consensus Service (HCS) sequence anchor, providing tamper-evident, independently verifiable proof of the supply fact at time of query.

## 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-attested-hedera-hbar-supply-facts-1effa076/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)