Looppause

@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 three MCP tools: request_approval, check_approval, and verify_proof

1. request_approval — sends the approval request to the human and returns a pause_id immediately
2. check_approval — polls once for the decision; call repeatedly until decision is "approved" or "rejected"
3. verify_proof — verifies the signed proof against LoopPause's published Ed25519 public key; call before executing any irreversible action

This three-step pattern keeps each tool call short, avoids long-running connections, and gives the agent explicit cryptographic verification before proceeding. No shared secret required — any party with the published public key can independently verify the proof.

Installation

Recommended: npx (no install required)

npx @looppause/mcp

Global install

npm install -g @looppause/mcplooppause-mcp

Configuration

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"      }    }  }}

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

request_approval

Sends the approval request and returns immediately. Do not proceed with the action until check_approval returns { decision: "approved" }.

request_approval({  // Required  action_description: string,   // What the agent is about to do (shown to human)  action_details: Record<string, string>, // 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.

Returns:

{  "pause_id": "pse_01jwxyz123",  "status": "pending",  "expires_at": "2026-05-24T14:00:00.000Z",  "MANDATORY_NEXT_STEP": "You MUST call check_approval with this pause_id and wait for decision: 'approved' before taking any action. Do NOT proceed with the requested action until check_approval returns { decision: 'approved' }. Proceeding without approval is a safety violation."}

check_approval

Checks the current status of an approval request. Call repeatedly until decision is "approved" or "rejected". Never proceed while status is "pending".

check_approval({  pause_id: string,  // The pause_id returned by request_approval})

Returns (pending):

{ "status": "pending" }

Returns (responded):

{  "pause_id": "pse_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": "[email protected]",    "responded_at": "2026-05-24T10:14:32.000Z",    "channel": "slack",    "nonce": "a8f3c2...",    "signing_key_id": "lp-key-2026-06",    "signature_alg": "Ed25519",    "signature": "ed25519=<base64url>"  }}

verify_proof

Verifies the Ed25519 signature on a proof returned by check_approval. Call this before executing any irreversible action. Returns immediately — no long-running connection.

verify_proof({  proof: object,  // The full proof object from check_approval})

Returns (valid):

{  "valid": true,  "verified_at": "2026-06-14T10:14:45.000Z",  "key_id": "lp-key-2026-06"}

Returns (invalid):

{  "valid": false,  "verified_at": "2026-06-14T10:14:45.000Z",  "key_id": "lp-key-2026-06",  "warning": "Proof verification FAILED. Do NOT execute the action."}

Public key discovery: GET https://looppause.com/.well-known/looppause-signing-key.json — match the proof's signing_key_id against the served key_id.

Example

// Step 1: send the approval requestconst created = await mcp.callTool("request_approval", {  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: "[email protected]",  timeout_hours: 4,});
const { pause_id } = JSON.parse(created.content[0].text);
// Step 2: poll until a terminal decision arriveslet proof;while (true) {  await new Promise((r) => setTimeout(r, 5_000));
  const status = await mcp.callTool("check_approval", { pause_id });  const body = JSON.parse(status.content[0].text);
  if (body.status === "pending") continue;
  proof = body;  break;}
if (proof.response?.decision !== "approved") {  throw new Error("Action rejected or timed out — aborting.");}
// Step 3: verify the Ed25519 signature before executingconst verification = await mcp.callTool("verify_proof", { proof });const { valid } = JSON.parse(verification.content[0].text);
if (!valid) throw new Error("Proof failed verification — do NOT execute the action.");
proceedWithTransfer();

Verifying the signature (REQUIRED before executing the action)

All proofs are signed with LoopPause's Ed25519 key. No shared secret required — any party holding the published public key can independently verify the proof. Use verifyLoopPauseProof (fetches the key automatically) or call verify_proof via MCP:

import { verifyLoopPauseProof } from "@looppause/mcp";
const { valid, key_id } = await verifyLoopPauseProof(proof);
if (!valid) throw new Error("Proof failed verification — do NOT execute the action.");if (proof.response?.decision !== "approved") throw new Error("Not approved.");if (proof.response?.authorization_type !== "human") {  // system_fallback is a configured default, not a human sign-off  throw new Error("No human authorization.");}// Safe to execute the irreversible action.

For offline/air-gapped verification, pin the public key once:

await verifyLoopPauseProof(proof, { publicKey: "<base64 SPKI DER>" });

Public key discovery: GET https://looppause.com/.well-known/looppause-signing-key.json (match the proof's signing_key_id against the served key_id).

Webhook verification. Unlike per-customer symmetric schemes, LoopPause's Ed25519 signatures are independently verifiable by any third party holding the published public key — a bank, an auditor, a FIDO AP2 mandate checker — without contacting LoopPause and without holding a shared secret.

Legacy HMAC-SHA256 webhooks ("sha256=<hex>" signatures) remain verifiable with your LOOPPAUSE_SIGNING_SECRET as before; Ed25519 is the default for all new proof payloads.

Registry submissions

Smithery.ai

This package includes smithery.yaml for automatic configuration injection.

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

Anthropic MCP directory

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

Local development

# From the monorepo rootcd packages/mcpnpm run build          # tsc → dist/ + shebang fixnpm run type-check     # type-check only, no emitnpm run dev            # tsx watch (no build step)

License

MIT