ProofSlip — AI Agent Verification API | Ephemeral Receipts for Agent Workflows

# ProofSlip > Ephemeral verification receipts for AI agent workflows. ProofSlip is a free API that creates short-lived proof tokens (receipts) that agents verify before acting. Receipts expire after 24 hours. No stale state, no replay attacks, no duplicate actions. ## API Base URL https://proofslip.ai ## Authentication Create receipts requires a Bearer token API key. Verification is public. Get a free key: POST /v1/auth/signup with {"email": "you@example.com", "source": "api"} ## Endpoints ### Create Receipt POST /v1/receipts Authorization: Bearer ak_... Request: { "type": "action | approval | handshake | resume | failure", "status": "success", "summary": "Refund of $42.00 issued to customer #8812", "payload": { ... }, "idempotency_key": "refund-8812-2026-03-23", "expires_in": 86400 } Response (201): { "receipt_id": "rct_...", "verify_url": "https://proofslip.ai/verify/rct_...", "created_at": "2026-03-23T12:00:00Z", "expires_at": "2026-03-24T12:00:00Z" } ### Verify Receipt GET /v1/verify/{receipt_id}?format=json Response (200): { "receipt_id": "rct_...", "valid": true, "type": "action", "status": "success", "summary": "Refund of $42.00 issued to customer #8812", "payload": { ... }, "expires_at": "2026-03-24T12:00:00Z", "expired": false } ### Check Status (lightweight poll) GET /v1/receipts/{receipt_id}/status Response (200): { "receipt_id": "rct_...", "status": "success", "is_terminal": true, "next_poll_after_seconds": null, "expires_at": "2026-03-24T12:00:00Z" } ## Receipt Types - action — Record a completed event (refund, deploy, notification) - approval — Gate an action on a human or agent decision - handshake — Coordinate between two agents before either acts - resume — Bookmark a safe continuation point in a pipeline - failure — Structured error record with bounded retry window ## MCP Server Install as an MCP tool for Claude, Cursor, or any MCP client: npx -y @proofslip/mcp-server ## Key