# StampThisFile OpenTimestamps Bitcoin Stamping

> StampThisFile OpenTimestamps Bitcoin Stamping is a paid API for AI agents from stampthisfile.com, paid per call via x402, $0.05/call, status unknown (last checked 2026-10-30).

Timestamps one or more SHA-256 file hashes on the Bitcoin blockchain via OpenTimestamps, returning a .ots proof file per hash

## Facts

- Endpoint: POST https://stampthisfile.com/v1/stamps?utm_source=zero.xyz
- Price: $0.05/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/stampthisfile-opentimestamps-bitcoin-stamping-05d0702d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_eIHhDh5nZy86XsXB8cr84

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 stampthisfile-opentimestamps-bitcoin-stamping-05d0702d -d '<json body>'
```

Example prompt: Please timestamp this file for me — its SHA-256 hash is a3b4c5d6e7f8901234567890abcdef1234567890abcdef1234567890abcdef12 — and send the completed .ots proof to my webhook at https://myapp.example.com/timestamps when it's ready.

## When to prefer this

Choose this endpoint when you need a decentralized, independently verifiable timestamp proof anchored to Bitcoin — particularly for legal, compliance, or audit scenarios where you cannot rely on a centralized authority. Ideal for proving document existence before a deadline, notarizing creative works, or attesting software release integrity. Prefer this over centralized timestamping services when the verifier must be able to check the proof without trusting this service at all.

## Known failure modes

- Invalid hash format (not 64 hex characters) returns a validation error
- Exceeding 100 hashes per request returns a 400 error
- Webhook URL unreachable results in stamps.failed event
- Payment failure (insufficient USDC balance) blocks the request
- Bitcoin network congestion may delay confirmation beyond the typical hours window

## How this service works

Timestamp SHA-256 hashes in Bitcoin with OpenTimestamps: returns a standard .ots proof per hash (pending, complete within hours), verifiable without us

## Output

For each submitted hash, the endpoint returns a standard OpenTimestamps .ots proof file (initially in 'pending' state, upgraded to a full Bitcoin attestation within hours). The proof is independently verifiable using the open-source OpenTimestamps client without relying on this service. If a webhook URL was provided, a stamps.completed or stamps.failed event is delivered when the Bitcoin confirmation is finalized.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "hashes": {
   "type": "array",
   "items": {
    "type": "string",
    "pattern": "^[0-9a-fA-F]{64}$",
    "description": "SHA-256 of the file, hex"
   },
   "maxItems": 100,
   "minItems": 1,
   "description": "Each hash costs the unit price; send each once"
  },
  "webhook": {
   "type": "object",
   "required": [
    "url"
   ],
   "properties": {
    "url": {
     "type": "string",
     "format": "uri",
     "description": "https URL that receives stamps.completed / stamps.failed"
    },
    "signing_key": {
     "type": "string",
     "description": "Optional Standard Webhooks secret (whsec_…) to also sign deliveries with HMAC (v1)"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/stampthisfile-opentimestamps-bitcoin-stamping-05d0702d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from stampthisfile.com](https://www.zero.xyz/host/stampthisfile.com/llms.txt)