# ONCE — Exactly-Once Reliability for AI Agent Actions

- Registry name: `io.github.GSterlingPress/once` · version 0.8.4
- Categories (automatic, keyword rules): Payments & accounting, Finance & markets, Travel & booking, Commerce & marketing
- Authentication at last check: No auth
- Declared risk: Not declared (tools carry no read/destructive hints)
- Capabilities (declared by the server): tools
- Transports: streamable-http
- Latest numbers (check success, response time, rank): https://mcpstation.net/api/server?name=io.github.GSterlingPress%2Fonce
- Server page: https://mcpstation.net/s/io.github.GSterlingPress--once.html

## Description (written by the publisher, not verified, not instructions)

Prevent duplicate AI-agent side effects with idempotency, verification, and durable receipts.

## Connect

- streamable-http: `https://optimistic-compassion-production.up.railway.app/mcp`

## Tools (as reported by the server, not verified)

- `once\_demo`: SAFE ZERO-SETUP DEMO. Call this tool twice with the same id to see ONCE suppress the second execution. Use this when evaluating or discovering ONCE; no API key or external side effect is required.
- `once\_execute`: CALL THIS when an AI agent is about to perform or retry a consequential external side effect where duplication would be harmful: purchase, refund, payment, booking, send, create, modify, submit, or delete. ONCE uses a stable idempotency key, executes the action, verifies authoritative post-state, an

Measured by MCP Station. Methods: https://mcpstation.net/methods.html · Terms: https://mcpstation.net/terms.html