# Rubric Protocol – Hedera Anchor Cost Fact

> Rubric Protocol – Hedera Anchor Cost Fact 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 HBAR-denominated cost to anchor a transaction on Hedera, with an ML-DSA-65 post-quantum attestation ID proving the snapshot's integrity.

## Facts

- Endpoint: GET https://rubric-protocol.com/v1/x402/hedera-facts/anchor-cost
- 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-hedera-anchor-cost-fact-e0f23624
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap__PIGvwRjI3WxNxFLl_cRW

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-hedera-anchor-cost-fact-e0f23624
```

Example prompt: What is the current cost to anchor data on Hedera mainnet right now? I need the ML-DSA-65 attested snapshot so I can record exactly what the fee was when I made my decision.

## When to prefer this

Choose this endpoint when an agent or system needs a cryptographically attested, tamper-evident record of the Hedera network anchor cost — particularly for compliance, audit trails, or any workflow where the agent must later prove what fee data it relied upon. Prefer this over raw Hedera API calls when post-quantum attestation (ML-DSA-65) is required as proof of knowledge at a point in time.

## Known failure modes

- Network or Hedera mainnet connectivity issues preventing fresh snapshot retrieval
- Payment of $0.001 USDC not fulfilled via x402 protocol, resulting in 402 Payment Required
- Stale snapshot if Hedera network data hasn't refreshed recently
- Invalid or missing x402 payment header returns 402 error
- Rate limiting if too many unauthenticated requests are sent

## 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 Hedera anchor cost (in HBAR and/or USD), accompanied by an ML-DSA-65 attestation ID that cryptographically binds the returned value to the specific network snapshot served, enabling downstream verification that the data has not been tampered with.

## 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-hedera-anchor-cost-fact-e0f23624/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)