All servers · Payments & accounting · Travel & booking

ONCE — Exactly-Once Reliability for AI Agent Actions

io.github.GSterlingPress/once · v0.8.4

Measured by MCP Station

Last check	Reachable
Checked at	—
Check success 7 / 30 days	—
First-try success 30 days	—
Median response	—
Lookups 30 days	—
Authentication	No auth
MCP version	2025-11-25
Rank score	—
Declared risk	Not declared (tools carry no read/destructive hints)
Capabilities declared	tools
Tool definitions	2 tools · with description 100% · input schema is an object 100% · read/destructive hints 0%

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

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

claude mcp add --transport http once https://optimistic-compassion-production.up.railway.app/mcp

{
  "mcpServers": {
    "once": {
      "url": "https://optimistic-compassion-production.up.railway.app/mcp"
    }
  }
}

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

Repository · Website · JSON · Text for agents · Registry updated 2026-09-13