# From source
git clone https://github.com/tejasghalsasi/helcim-mcp.git
cd helcim-mcp
pnpm install
pnpm rebuild esbuild   # required: pnpm 11 blocks esbuild's postinstall by default
pnpm build

# Set your token (never commit it)
export HELCIM_API_TOKEN="your_token_here"

# Run over stdio
node packages/mcp/dist/index.js

{
  "mcpServers": {
    "helcim": {
      "command": "node",
      "args": ["/absolute/path/to/helcim-mcp/packages/mcp/dist/index.js"],
      "env": {
        "HELCIM_API_TOKEN": "your_token_here"
      }
    }
  }
}

flowchart LR
    subgraph Client["MCP Client (LLM)"]
        A[Agent]
    end

    subgraph Server["@helcim-mcp/server"]
        M[MCP Server<br/>stdio transport]
        T[Read-only tools<br/>13 tools]
    end

    subgraph Core["@helcim-mcp/core"]
        C[HelcimClient]
        H[HelcimHttpClient<br/>auth, idempotency,<br/>rate-limit, redaction]
        E[Normalized errors]
    end

    subgraph Webhooks["@helcim-mcp/webhooks"]
        W[HelcimWebhookVerifier<br/>HMAC-SHA256, replay protection]
    end

    subgraph Helcim["Helcim API"]
        API[api.helcim.com/v2]
    end

    A -->|JSON-RPC over stdio| M
    M --> T
    T --> C
    C --> H
    H -->|HTTPS + api-token| API
    W -.->|verifies signed events| API

helcim-mcp/
├── packages/
│   ├── core/       # Typed Helcim API client (read-safe)
│   ├── mcp/        # MCP server (read-only tools)
│   ├── webhooks/   # Webhook verifier
│   └── fixtures/   # Deterministic mock responses + test vectors
├── examples/       # Copy-paste usage examples
├── docs/           # Architecture, env reference, troubleshooting
└── scripts/        # Smoke test, CI helpers

list_invoices(status: "DUE")
→ { count: 2, invoices: [
    { invoiceId: 28658838, invoiceNumber: "INV1000", status: "DUE", currency: "CAD", customerId: 2488717 },
    { invoiceId: 28658839, invoiceNumber: "INV1001", status: "DUE", currency: "USD", customerId: 2488718 }
  ] }

list_card_transactions(limit: 5)
→ { count: 2, transactions: [
    { transactionId: 25557533, status: "APPROVED", type: "purchase", amount: 100.99, currency: "CAD", cardType: "MC", customerCode: "CST1000" },
    { transactionId: 25557534, status: "DECLINED", type: "purchase", amount: 250.00, currency: "CAD", cardType: "VI", customerCode: "CST1001" }
  ] }

get_invoice(invoiceId: 28658838) → { customerId: 2488717, ... }
get_customer(customerId: 2488717) → { customerCode: "CST1000", businessName: "Acme Widgets Ltd", ... }

list_subscriptions(hasFailedPayments: true)
→ { count: 1, subscriptions: [ { id: 42, status: "ACTIVE", hasFailedPayments: true, customerCode: "CST1000", ... } ] }

→ Error: Unknown tool: process_refund

import { HelcimWebhookVerifier } from '@helcim-mcp/webhooks';

const verifier = new HelcimWebhookVerifier(process.env.HELCIM_VERIFIER_TOKEN!);

// In your webhook handler (e.g. Next.js route handler):
export async function POST(req: Request) {
  const body = await req.text();
  const headers = Object.fromEntries(req.headers.entries());
  try {
    const verified = verifier.verify(headers, body);
    // verified.event.type === 'cardTransaction' | 'terminalCancel'
    return new Response('ok', { status: 200 });
  } catch (err) {
    return new Response('invalid signature', { status: 401 });
  }
}

pnpm install
pnpm rebuild esbuild  # pnpm 11 blocks esbuild's postinstall by default
pnpm build        # build all packages
pnpm test         # run all tests
pnpm typecheck    # type-check all packages
pnpm lint         # prettier check
pnpm smoke        # verify the built server exposes only read-only tools