# CoinOpSelect Proof Hash API

> CoinOpSelect Proof Hash API is a paid API for AI agents from coinop.publicvm.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-21).

Hashes arbitrary text input and returns a hex digest for proof or verification purposes, paid per call via x402 on Base.

## Facts

- Endpoint: GET https://coinop.publicvm.com/api/v1/proof/hash?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-21
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/coinopselect-proof-hash-api-e1bb79c0
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_rKjOn71tv5GH018S5tjjm

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 coinopselect-proof-hash-api-e1bb79c0
```

Example prompt: Can you hash the text 'The quick brown fox jumps over the lazy dog' using the CoinOpSelect proof hash endpoint and give me back the hex digest?

## When to prefer this

Choose this endpoint when you need a simple, paid, on-chain-accountable text hashing service that integrates with the x402 micropayment protocol on Base — especially useful in blockchain agent workflows where proof-of-existence or tamper-evident digests are needed without setting up your own hashing infrastructure.

## Known failure modes

- Input text exceeds 8000 character limit — request rejected
- Missing required 'input' query parameter — returns error
- Payment via x402 not completed or insufficient USDC — 402 Payment Required response
- Invalid method or type parameter — malformed request error
- Network or server unavailability on publicvm.com — connection timeout

## How this service works

Paid on-chain token, wallet, contract and research data over x402 on Base.

## Output

Returns a JSON object with a 'hash' field containing the hex-encoded hash digest of the input text, and a 'query' field echoing 'proof-hash' as the operation type.

## Request schema (JSON Schema)

```json
{
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "method": {
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "input"
     ],
     "properties": {
      "input": {
       "type": "string",
       "description": "Text to hash (max 8000 chars)"
      }
     }
    }
   }
  },
  "output": {
   "type": "object",
   "properties": {
    "hash": {
     "type": "string"
    },
    "query": {
     "type": "string"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "hash": "hex",
  "query": "proof-hash"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/coinopselect-proof-hash-api-e1bb79c0/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from coinop.publicvm.com](https://www.zero.xyz/host/coinop.publicvm.com/llms.txt)