@looppause/mcp

@looppause/mcp

MCP server for LoopPause — pause AI agent execution and route approval requests to humans via Slack or email. The agent receives a cryptographically signed proof of the human's decision and resumes.

"The missing primitive so agents don't go rogue — or die waiting for approval."

What it does

Exposes a single MCP tool: pause_agent_action

When called, the tool:

• POSTs an approval request to the LoopPause API
• Delivers a Slack Block Kit card and/or an email to the specified recipient
• Blocks the agent (polls every 5 seconds) until the human responds
• Returns the full signed response payload — decision, comment, structured fields, HMAC signature

The agent can verify the signature with its LOOPPAUSE_SIGNING_SECRET before trusting the decision.

Installation

Recommended: npx (no install required)

npx @looppause/mcp

Global install

npm install -g @looppause/mcp
looppause-mcp

Configuration

Environment variable	Required	Description
LOOPPAUSE_API_KEY	✅ Yes	Your LoopPause API key (sk_live_…)
LOOPPAUSE_API_URL	No	Override the API base URL (default: https://api.looppause.com)

Get your API key at looppause.com/dashboard.

Usage in Claude Code

Add to your .claude/settings.json (or ~/.claude/settings.json for global):

{
  "mcpServers": {
    "looppause": {
      "command": "npx",
      "args": ["-y", "@looppause/mcp"],
      "env": {
        "LOOPPAUSE_API_KEY": "sk_live_your_key_here"
      }
    }
  }
}

Claude Code will automatically discover and offer the pause_agent_action tool.

Usage in Cursor

Add to your Cursor MCP configuration:

{
  "mcpServers": {
    "looppause": {
      "command": "npx",
      "args": ["-y", "@looppause/mcp"],
      "env": {
        "LOOPPAUSE_API_KEY": "sk_live_your_key_here"
      }
    }
  }
}

Tool reference

pause_agent_action

pause_agent_action({
  // Required
  action_description: string,   // What the agent is about to do (shown to human)
  action_details: object,       // Structured key-value context (amount, vendor, etc.)

  // At least one recipient required
  recipient_email?: string,     // Email address
  recipient_slack?: string,     // Slack channel (#approvals) or user ID (U12345)

  // Optional
  timeout_hours?: number,       // Default 24, max 168 (1 week)
})

When both recipient_slack and recipient_email are provided, Slack is the primary channel and email is the fallback.

Example

// In your agent — before an irreversible action
const result = await mcp.callTool("pause_agent_action", {
  action_description: "Transfer £12,450 to Globex Corp for invoice INV-2341",
  action_details: {
    vendor: "Globex Corp",
    amount: 12450,
    currency: "GBP",
    invoice_ref: "INV-2341",
  },
  recipient_slack: "#finance-approvals",
  recipient_email: "[e-mail]",
  timeout_hours: 4,
});

Response

On approval or rejection the tool returns a JSON string:

{
  "pause_id": "pause_01jwxyz123",
  "agent_id": "mcp-agent",
  "status": "responded",
  "created_at": "2026-05-24T10:00:00.000Z",
  "expires_at": "2026-05-24T14:00:00.000Z",
  "response": {
    "decision": "approved",
    "comment": "PO number: PO-2341",
    "fields": { "po_number": "PO-2341" },
    "responder": "[e-mail]",
    "responded_at": "2026-05-24T10:14:32.000Z",
    "channel": "slack",
    "nonce": "a8f3c2...",
    "signature": "sha256=4d9f1a..."
  }
}

Verify the signature against your LOOPPAUSE_SIGNING_SECRET before proceeding:

import { createHmac, timingSafeEqual } from "node:crypto";

function verifyDecision(payload: string, receivedSig: string): boolean {
  const body = JSON.parse(payload);
  const { signature: _, ...unsigned } = body.response;
  const canonical = JSON.stringify(
    Object.fromEntries(Object.entries(unsigned).sort())
  );
  const expected = "sha256=" +
    createHmac("sha256", process.env.LOOPPAUSE_SIGNING_SECRET!)
      .update(canonical)
      .digest("hex");
  const a = Buffer.from(expected);
  const b = Buffer.from(receivedSig);
  return a.length === b.length && timingSafeEqual(a, b);
}

Terminal states

Return value	Meaning
JSON string	Human responded — check response.decision for "approved" or "rejected"
"The approval request timed out…"	No response within timeout_hours
"The approval request was cancelled."	Pause was manually expired

Registry submissions

Smithery.ai

This package includes smithery.yaml for automatic configuration injection.

• Fork or publish @looppause/mcp to npm
• Submit at smithery.ai/new → enter @looppause/mcp
• Smithery will read smithery.yaml and present a UI for users to enter their API key

Anthropic MCP directory

• Ensure the package is published to npm as @looppause/mcp
• Submit via the Anthropic MCP directory form or the directory submission page when available
• List as: @looppause/mcp — LoopPause human-in-the-loop approval tool

Local development

# From the monorepo root
cd packages/mcp
npm run build          # tsc → dist/
npm run type-check     # type-check only, no emit
npm run dev            # tsx watch (no build step)

License

MIT