ONCE — Exactly-Once Reliability for AI Agent Actions MCP Server

What the code does

We read the source, 3 d ago · tools taken from the live server · rules ccca72095570

A value the model can set ends up inside a file or shell call. That is not a flaw by itself — for a terminal server it is the job — but it is where things go wrong when it is not.

      return JSON.parse(await fs.readFile(this.receiptPath(key), 'utf8'));

What this server is able to do. For an MCP server this is often the job itself — a terminal server runs commands because that is what it is for. Listed so you know what you are plugging in, not as an accusation.

…,'usage');this.lock=new FileLock({locksDir:path.join(dataDir,'usage-locks')})}usagePath(keyId,period=monthKey()){return path.join(this.usageDir,keyId,`${period}.json`)}async get(keyId,period=monthKey()){return readJson(this.usagePath(keyId,period),{keyId,period,calls:0,verified:0…

Is this your server and something here is wrong? Tell us — corrections are free and do not require a plan.

Connect this server

Endpoint below is the one we actually reach during checks — not the one copied from a README. Last verified 11 min ago.

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

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

[mcp_servers.once]
url = "https://optimistic-compassion-production.up.railway.app/mcp"

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

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

Available tools 2

Read directly from the server with tools/list, grouped by what they act on. If a tool disappears, we record the date.

Endpoints