# Rubric Protocol – Hedera HCS Activity Facts

> Rubric Protocol – Hedera HCS Activity Facts is a paid API for AI agents from rubric-protocol.com, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-14).

Returns ML-DSA-65-attested Hedera Consensus Service (HCS) topic activity and network state facts, providing tamper-evident proof of what an agent knew at decision time.

## Facts

- Endpoint: GET https://rubric-protocol.com/v1/x402/hedera-facts/hcs-activity
- Price: $0.001/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-hedera-hcs-activity-facts-eff93395
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_kJfDK4CQHndOQCA-3GHow

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-hcs-activity-facts-eff93395
```

Example prompt: Fetch me the latest attested HCS activity snapshot from Rubric Protocol so I have a post-quantum-signed record of Hedera Consensus Service topic throughput and state I can include as proof in my audit trail.

## When to prefer this

Choose this endpoint when you need cryptographically attested, post-quantum-signed HCS topic activity data from the Hedera network and require provable, tamper-evident records of what your agent observed — especially for compliance, audit, or accountability workflows where you must prove the information state at decision time. Prefer this over generic Hedera explorers or non-attested data sources when the verifiability of the data matters.

## Known failure modes

- Payment not received or malformed x402 header — returns 402 Payment Required
- Hedera network connectivity issue — snapshot may be stale or unavailable, returns 503
- Invalid or missing required input fields — returns 400 Bad Request
- Rate limiting or quota exceeded — returns 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 snapshot of Hedera Consensus Service topic activity and throughput metrics, accompanied by an ML-DSA-65 (post-quantum) attestation ID that cryptographically binds the agent to the specific snapshot served. The attestation ID can be stored as tamper-evident proof of the observed state at the time of the call.

## 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-hcs-activity-facts-eff93395/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)