once

once is an MCP server for Claude Code, Codex, Cursor, Gemini CLI, OpenCode from GSterlingPress/once-api. Its token cost is not measured, scanned A, original, no licence file.

A remote tool that prevents an AI agent from repeating an action that has already taken effect. It uses idempotency, verification, and saved receipts to track completed side effects.

In plain words
What is it for?
Safely handling actions where duplicates would matter, while verifying results and keeping durable records of completed operations.
Why use it?
It reduces duplicate changes when an agent retries after a timeout, interruption, or uncertain result.

MCP server for Claude CodeCodexCursorGemini CLIOpenCode

Written for no agent in particular: it speaks MCP, so any client can run it.

Good fit Safely handling actions where duplicates would matter, while verifying results and keeping durable records of completed operations.

Compare 6 mcp servers from other repositories ↓
Install with agentmods
npx agentmods add mcp/gsterlingpress/once-api/once
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Clone the repo
git clone --depth 1 https://github.com/GSterlingPress/once-api

Made for: Claude Code, Codex, Cursor, Gemini CLI, OpenCode.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for once

README.md
[![agentmods](https://agentmods.dev/badge/mcp/gsterlingpress/once-api/once/github.svg)](https://agentmods.dev/mcp/gsterlingpress/once-api/once)
Your own site
<a href="https://agentmods.dev/mcp/gsterlingpress/once-api/once"><img src="https://agentmods.dev/badge/mcp/gsterlingpress/once-api/once/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for once

Your own site · 80×15
<a href="https://agentmods.dev/mcp/gsterlingpress/once-api/once"><img src="https://agentmods.dev/badge/mcp/gsterlingpress/once-api/once.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session not measured What this adds to a session before it is invoked.
When invoked not measured Not applicable: nothing here is loaded into a session.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin unknown No closer match found in the catalogue.
Security

Grade A, and why

once scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

server.json · 6 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 1mo ago First seen · 6 lines scan A fc2dcab47f9f

Subscribe to this mod's changes

once is an MCP server published in the GitHub repository GSterlingPress/once-api (0 stars, last pushed 1mo ago), with no licence file. Its token cost is not measured: an MCP server costs its tool schemas, not its config file. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.