# Onchain Evidence

> Onchain Evidence is a paid API for AI agents from phion.systems, paid per call via x402, $0.004/call, status unknown (last checked 2026-10-02).

Captures public blockchain explorer or RPC data as immutable evidence with cryptographic content hashes

## Facts

- Endpoint: POST https://phion.systems/v1/paid/trust/onchain-evidence?utm_source=zero.xyz
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/onchain-evidence-d75599fb
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_fhPuUU6Ud7hO4GaBC7d1K

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 onchain-evidence-d75599fb -d '<json body>'
```

Example prompt: Capture and hash this Etherscan transaction page as immutable on-chain evidence so I have a tamper-evident record of its state right now: https://etherscan.io/tx/0xabc123...

## When to prefer this

Use this endpoint when you need cryptographically verifiable, immutable proof of on-chain data from public blockchain explorers or RPC sources — especially for compliance, dispute resolution, or audit trails. Prefer this over simple web scraping when tamper-evidence and content integrity hashes are required, and over general blockchain queries when you need a signed, timestamped evidence artifact rather than raw data.

## Known failure modes

- Invalid or inaccessible explorer URL returns an error indicating the source could not be fetched
- RPC endpoint unavailable or rate-limited results in a capture failure
- Malformed input schema causes a 400-level validation error
- Content hash cannot be computed if the source returns dynamic or non-deterministic content
- Payment not processed via x402 protocol results in a 402 Payment Required response

## How this service works

Capture supplied public explorer or RPC evidence with immutable content hashes

## Output

Returns an immutable evidence record containing the captured public explorer or RPC data, a cryptographic content hash of that data, a timestamp, and provenance metadata — allowing any party to verify that the captured content has not been altered since capture.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input",
  "output"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "body"
   ],
   "properties": {
    "body": {
     "type": "object",
     "additionalProperties": true
    }
   }
  },
  "output": {
   "type": "object",
   "required": [
    "example"
   ],
   "properties": {
    "example": {
     "type": "object",
     "additionalProperties": true
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json"
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/onchain-evidence-d75599fb/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from phion.systems](https://www.zero.xyz/host/phion.systems/llms.txt)