Junto

Junto is a universal MCP server that exposes a standardized payment toolkit to any compatible client, routes transactions to the right provider, enforces spending safeguards, supports human-in-the-loop approval for high-value operations, and logs every action for auditability. It enables AI assistants and agents to pay invoices, request payments, and transfer funds across diverse rails with consistent behavior and governance.

How to use

You connect your MCP client (such as Claude, Cursor, or a custom agent) to Junto through the MCP protocol. Junto handles routing to the appropriate provider based on currency, country, and rail, applies guardrails to keep spending within defined limits, and can require human confirmation for high-value transactions. You can inspect the audit trail to track every action taken by agents.

Key actions you can perform with Junto include paying funds to a destination, creating payment requests or invoices, checking status, issuing refunds, and querying balances. You can also list configured providers and review current spending limits. When you set up agents, you can rely on Junto to enforce daily caps, per-transaction caps, and optional HITL prompts for approvals.

How to install

Prerequisites: you need Node.js and npm installed on your system. Confirm you can install global npm packages and run commands from your shell.

Step 1: Install the MCP server globally.

npm install -g junto-mcp

Step 2: Set your Woovi provider API key as an environment variable. This enables Junto to communicate with the payment provider.

export WOOVI_APP_ID="your-woovi-app-id"

Step 3: Run the MCP server. This starts the Junto MCP server so your MCP clients can connect.

pjunto-mcp

Step 4: Add Junto to your MCP client configuration. The example below shows how to wire Junto into Claude Desktop or Cursor by providing the MCP server entry under mcpServers.

{
  "mcpServers": {
    "junto": {
      "command": "npx",
      "args": ["-y", "junto-mcp"],
      "env": {
        "WOOVI_APP_ID": "your-woovi-app-id"
      }
    }
  }
}

Guardrails and configuration overview

All amounts use the smallest currency unit (cents) to avoid floating point errors. Guardrails enforce safe spending and provide control when agents attempt transactions beyond set thresholds.

Key guardrails you can configure include daily spend limits, per-transaction caps, and a threshold that requires human confirmation. If an attempt exceeds the confirmation threshold, Junto pauses and presents the user with a confirmation prompt before proceeding.

Environment variables you can tune include the daily limit, per-transaction limit, confirmation threshold, allowed providers, and allowed destinations. These controls govern how and when agents can execute payments.

Providers and capabilities

Junto supports multiple providers. The initial integration includes Woovi/OpenPix for Pix-based payments in Brazil, with other providers like Belvo, Stripe, Wise, Mercado Pago, and PayPal planned as future options. Each provider exposes its own rails (payment methods) and settlement behavior, with Junto responsible for selecting the right option based on the transaction details.

You can view the configured providers and their capabilities from the MCP client once Junto is running. Junto logs every action to the audit ledger for traceability.

Demo scenario

A user says: Pay R$25 to maria@email.com via Pix. The agent parses the request, renders a confirmation prompt, and awaits your approval. After you confirm, the agent completes the payment through the chosen provider, and you receive a final status indicating completion along with a transaction ID.

Testing and auditing

You can run tests to validate guardrails and flows. Junto creates an audit entry for every transaction in a JSONL ledger, including timestamps, action types, amounts, currencies, providers, destinations, and final status. This ledger supports accountability and post-transaction review.

Notes about adding additional providers and extending functionality

To extend Junto with new providers, you implement a provider class that adheres to the PaymentProvider interface and register it in the MCP server index. You can adapt routing logic to balance speed, cost, and reliability, and you can build HITL patterns into the confirmation flow to fit your operational needs.

Security and best practices

Treat API keys and access tokens as secrets. Use separate keys for development and production, rotate credentials regularly, and restrict access to the MCP server and its logs. Monitor the audit log for anomalies and ensure HITL prompts are clearly presented to users when required.

Roadmap and contributing guidance

The project plans to add more providers, expand multi-currency support, enhance routing strategies, and improve dashboards and compliance guidance. Contributions are welcome for provider adapters, routing logic, HITL patterns, security audits, multi-currency workflows, and documentation.

License

MIT License.

Available tools

pay

Send money to a destination (Pix key, email, IBAN, etc.).

charge

Create a payment request, invoice, or QR code.

status

Check payment status by correlation ID.

refund

Reverse a completed transaction.

balance

Check available funds on a provider.

providers

List configured providers and their capabilities.

limits

Show spending limits and today's usage.