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."

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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.

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Installation

Recommended: npx (no install required)

npx @looppause/mcp

Global install

npm install -g @looppause/mcp

looppause-mcp

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Configuration

Get your API key at looppause.com/dashboard.

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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" } } } }

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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 , // 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." }

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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": "sarah@company.com", "responded_at": "2026-05-24T10:14:32.000Z", "channel": "slack", "nonce": "a8f3c2...", "signing_key_id": "lp-key-2026-06", "signature_alg": "Ed25519", "signature": "ed25519= " } }

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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.

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Example

// Step 1: send the approval request

const 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: "sarah@company.com", timeout_hours: 4, });

const { pause_id } = JSON.parse(created.content[0].text);

// Step 2: poll until a terminal decision arrives let 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 executing const 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();

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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= " signatures) remain verifiable with your LOOPPAUSE_SIGNING_SECRET as before; Ed25519 is the default for all new proof payloads.

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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

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Local development

# From the monorepo root

cd packages/mcp npm run build # tsc → dist/ + shebang fix npm run type-check # type-check only, no emit npm run dev # tsx watch (no build step)

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License

MIT