# Receipts

Every Zambo tool call returns a verifiable receipt with a UUID, tool name, UTC timestamp, SHA-256 hash of the exact output bytes, execution status, and a public URL where anyone can check the record without an account.

## How to verify one

1. Open the public receipt URL.
2. Compare the SHA-256 value in the receipt with a fresh hash of the returned output bytes.
3. Treat any changed byte as a changed result.

## What it proves

- A specific tool ran with specific inputs at a specific time.
- The output quoted is exactly what came back, byte for byte.

## What it does not prove

- Correctness. The receipt is proof of observed execution, not a claim that the output is right.
- Anything outside the recorded call.

Whole-job receipts use `journal_log` and public run pages to provide one checkable timeline per job.