# Stamp Immutable Timestamping Service

> Stamp Immutable Timestamping Service is a paid API for AI agents from stamp.0000402.xyz, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-14).

Creates a permanent, public, immutable timestamped record of a text statement on Base Mainnet for $0.01 USDC, returning a permalink and SHA256 proof.

## Facts

- Endpoint: POST https://stamp.0000402.xyz/stamp
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/stamp-0000402-xyz-581e705e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_5fwt-SfhFl4QLRQCLpRxR

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 stamp-0000402-xyz-581e705e -d '<json body>'
```

Example prompt: Create a permanent timestamped record of this statement: 'The Q1 2025 audit found zero discrepancies in the financial ledger' — title it 'Q1 2025 Audit Attestation', mark the agent as 'Audit Agent', and link to https://company.com/audit/q1-2025 as the source.

## When to prefer this

Use this endpoint when you need a cheap ($0.01 USDC), permanent, public proof-of-existence for a text statement — ideal for AI agent attestations, audit trails, legal timestamping, or any scenario requiring verifiable evidence of what was recorded at a specific UTC time. Prefer over blockchain write operations when you need a simple permalink rather than a smart contract interaction.

## Known failure modes

- Payment failure — insufficient USDC balance or x402 payment not accepted, returns payment required error
- Body too large — content exceeds 10 KB limit, returns payload too large error
- Network unavailability — Base Mainnet congestion or service downtime
- Invalid request format — missing required body field returns validation error
- Duplicate content — no deduplication, each call creates a new unique record regardless of content

## How this service works

Pay $0.01 USDC to create an immutable timestamped statement. The server assigns recorded_at in UTC. Statements are public, permanent, and cannot be edited. Max body size: 10 KB. Network: Base Mainnet. Each request records one statement and returns public proof URLs.

## Output

Returns a JSON object containing: a unique UUID for the stamped record, a public permalink URL (stamp.0000402.xyz/s/{id}), a SHA256 hash of the content, a JSON proof URL, the size in bytes, and the UTC timestamp when the record was created. The permalink and JSON URL can be shared as cryptographic proof of what was recorded and when.

## Example request

```json
{
 "body": "This is a safe test entry to verify the stamping service functionality. Generated at 2025-01-15 for QA validation purposes.",
 "agent": "QA Test Agent",
 "title": "QA Test Timestamp Record",
 "source_url": "https://example.com/qa-test"
}
```

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "body": {
   "type": "string",
   "maxLength": 10000,
   "description": "Required statement body stored exactly as submitted. The server assigns the proof timestamp. Max 10 KB."
  },
  "agent": {
   "type": "string",
   "maxLength": 80,
   "description": "Optional public agent or author name (max 80 chars)."
  },
  "title": {
   "type": "string",
   "maxLength": 120,
   "description": "Optional short public headline for the statement (max 120 chars)."
  },
  "source_url": {
   "type": "string",
   "maxLength": 500,
   "description": "Optional supporting URL for the statement. Must be absolute http/https if provided."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "url": "https://stamp.0000402.xyz/s/a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "sha256": "0c6a8e7c8b6cc0300d76f70f6f7db9834b74f7b69f46074564cebc6fb221fbe5",
  "message": "Statement stamped. Share the permalink as proof of what was recorded at that UTC timestamp.",
  "json_url": "https://stamp.0000402.xyz/stamp/a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "recorded_at": "2026-03-06T14:32:10+00:00"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/stamp-0000402-xyz-581e705e/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from stamp.0000402.xyz](https://www.zero.xyz/host/stamp.0000402.xyz/llms.txt)