ynab-mcp-server

A Model Context Protocol (MCP) server built with mcp-framework. This MCP provides tools for interacting with your YNAB budgets setup at https://ynab.com

In order to have an AI interact with this tool, you will need to get your Personal Access Token from YNAB: https://api.ynab.com/#personal-access-tokens. When adding this MCP server to any client, you will need to provide your personal access token as YNAB_API_TOKEN. This token is never directly sent to the LLM. It is stored privately in an environment variable for use with the YNAB api.

Setup

Specify env variables:

YNAB_API_TOKEN (required)
YNAB_BUDGET_ID (optional)

Goal

The goal of the project is to be able to interact with my YNAB budget via an AI conversation. There are a few primary workflows I want to enable:

Workflows:

First time setup

be prompted to select your budget from your available budgets. If you try to use another tool first, this prompt should happen asking you to set your default budget.
- Tools needed: ListBudgets

Manage overspent categories

Adding new transactions

Approving transactions

Check total monthly spending vs total income

Auto-distribute ready to assign funds based on category targets

Current state

Available tools:

ListBudgets - lists available budgets on your account
BudgetSummary - provides a summary of categories that are underfunded and accounts that are low
GetUnapprovedTransactions - retrieve all unapproved transactions
CreateTransaction - creates a transaction for a specified budget and account.
- example prompt: Add a transaction to my Ally account for $3.98 I spent at REI today
- requires GetBudget to be called first so we know the account id
ApproveTransaction - approves an existing transaction in your YNAB budget
- requires a transaction ID to approve
- can be used in conjunction with GetUnapprovedTransactions to approve pending transactions
- After calling get unapproved transactions, prompt: approve the transaction for $6.95 on the Apple Card

be able to approve multiple transactions with 1 call
updateCategory tool - or updateTransaction more general tool if I can get optional parameters to work correctly with zod & mcp framework
move off of mcp framework to use the model context protocol sdk directly?

Quick Start

# Install dependencies
npm install

# Build the project
npm run build

Project Structure

ynab-mcp-server/
├── src/
│   ├── tools/        # MCP Tools
│   └── index.ts      # Server entry point
├── .cursor/
│   └── rules/        # Cursor AI rules for code generation
├── package.json
└── tsconfig.json

Adding Components

The YNAB sdk describes the available api endpoints: https://github.com/ynab/ynab-sdk-js.

YNAB open api specification is here: https://api.ynab.com/papi/open_api_spec.yaml. This can be used to prompt an AI to generate a new tool. Example prompt for Cursor Agent:

create a new tool based on the readme and this openapi doc: https://api.ynab.com/papi/open_api_spec.yaml

The new tool should get the details for a single budget

You can add more tools using the CLI:

# Add a new tool
mcp add tool my-tool

# Example tools you might create:
mcp add tool data-processor
mcp add tool api-client
mcp add tool file-handler

Tool Development

Example tool structure:

import { MCPTool } from "mcp-framework";
import { z } from "zod";

interface MyToolInput {
  message: string;
}

class MyTool extends MCPTool<MyToolInput> {
  name = "my_tool";
  description = "Describes what your tool does";

  schema = {
    message: {
      type: z.string(),
      description: "Description of this input parameter",
    },
  };

  async execute(input: MyToolInput) {
    // Your tool logic here
    return `Processed: ${input.message}`;
  }
}

export default MyTool;

Publishing to npm

Update your package.json:
- Ensure name is unique and follows npm naming conventions
- Set appropriate version
- Add description, author, license, etc.
- Check bin points to the correct entry file

Build and test locally:

npm run build
npm link
ynab-mcp-server  # Test your CLI locally

Login to npm (create account if necessary):
```
npm login
```
Publish your package:
```
npm publish
```

After publishing, users can add it to their claude desktop client (read below) or run it with npx

Using with Claude Desktop

Installing via Smithery

To install YNAB Budget Assistant for Claude Desktop automatically via Smithery:

npx -y @smithery/cli install @calebl/ynab-mcp-server --client claude

Local Development

Add this configuration to your Claude Desktop config file:

MacOS: ~/Library/Application Support/Claude/claude_desktop_config.json Windows: %APPDATA%/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "ynab-mcp-server": {
      "command": "node",
      "args":["/absolute/path/to/ynab-mcp-server/dist/index.js"]
    }
  }
}

After Publishing