ProofSlip

Portable proof objects for agent workflows.

24-hour ephemeral receipts that let agents verify what happened before deciding what happens next. Create a receipt, check it later, let it expire. That's it.

Agents should not continue based on assumptions when they can continue based on receipts.

Live Site | API Docs | Example Receipt | MCP Server | llms.txt

The Problem

Agentic workflows break in predictable ways: duplicate side effects, unclear approval states, unsafe retries, ambiguous resumability. Teams currently solve this with raw logs, brittle flags, ad hoc DB rows, and hand-rolled retry logic.

ProofSlip replaces all of that with a single primitive: a short-lived, machine-readable receipt — a portable proof object that travels with the workflow and answers the questions agents actually ask:

• Did this action already happen?
• Was the request approved?
• Is retry safe?
• Should I continue, wait, or escalate?

How It Works

1. Agent completes a step → creates a receipt (POST /v1/receipts)
2. Next agent (or same agent later) → verifies the receipt before acting
3. Receipt expires after 24 hours → no cleanup burden

Every receipt includes polling guidance (is_terminal, next_poll_after_seconds) so agents know whether to stop, wait, or keep checking.

Receipt Types

| Type | Use Case | |------|----------| | action | Record that something happened (always terminal) | | approval | Track pending/approved/rejected decisions | | handshake | Two agents confirming shared context | | resume | Bookmark for safe workflow continuation | | failure | Structured failure with retry guidance (always terminal) |

Quick Start

1. Get an API Key

curl -X POST https://proofslip.ai/v1/auth/signup \
  -H "Content-Type: application/json" \
  -d '{"email": "you@example.com"}'

Save the returned key immediately — it cannot be retrieved later.

2. Create a Receipt

curl -X POST https://proofslip.ai/v1/receipts \
  -H "Authorization: Bearer ak_your_key_here" \
  -H "Content-Type: application/json" \
  -d '{
    "type": "action",
    "status": "success",
    "summary": "Sent welcome email to user@example.com",
    "ref": {
      "workflow_id": "onboarding-123",
      "agent_id": "email-agent"
    }
  }'

Returns:

{
  "receipt_id": "rct_abc123...",
  "type": "action",
  "status": "success",
  "summary": "Sent welcome email to user@example.com",
  "verify_url": "https://proofslip.ai/verify/rct_abc123...",
  "created_at": "2026-03-25T12:00:00.000Z",
  "expires_at": "2026-03-26T12:00:00.000Z",
  "is_terminal": true,
  "next_poll_after_seconds": null
}

3. Verify Before Acting

# JSON (for agents)
curl https://proofslip.ai/v1/verify/rct_abc123?format=json

# HTML (for humans — paste the verify_url in a browser)

4. Poll Non-Terminal Receipts

For approval workflows where a receipt starts as pending:

# Lightweight status check (no payload, no ref — just state)
curl https://proofslip.ai/v1/receipts/rct_abc123/status

{
  "receipt_id": "rct_abc123...",
  "status": "pending",
  "is_terminal": false,
  "next_poll_after_seconds": 30,
  "expires_at": "2026-03-26T12:00:00.000Z"
}

API Reference

| Method | Endpoint | Auth | Description | |--------|----------|------|-------------| | POST | /v1/receipts | API Key | Create a receipt | | GET | /v1/verify/:id | None | Verify a receipt (JSON or HTML) | | GET | /verify/:id | None | Shortcut verify (same behavior) | | GET | /v1/receipts/:id/status | None | Lightweight polling endpoint | | POST | /v1/auth/signup | None | Get an API key | | GET | /health | None | Health check |

Create Receipt Fields

| Field | Required | Description | |-------|----------|-------------| | `type

... View full README on GitHub