Splitwise MCP Server — Control Splitwise With Plain English

"Add a ₩45,000 dinner, I paid, split equally." Done. No app. No tapping. No math.

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Why I Built This

I was about to head on a trip with friends and already dreading the expense tracking.

You know how it goes — someone pays for dinner, someone else grabs the cab, another person covers the hotel deposit. By day two, you've lost track. So you open Splitwise, tap through four screens, type the amount, select the people, pick who paid, hit save. Then do it again for the next thing. And the next.

I thought: I'm already using Claude for everything else. What if I could just tell it what happened, and it handles Splitwise for me?

So I built this over a weekend. It's a small Python server that connects Claude AI directly to your Splitwise account. You talk to Claude like a human, and it does the Splitwise work for you — adding expenses, checking balances, recording settlements, fixing mistakes.

No switching apps. No manual entry. Just say what happened.

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What It Feels Like to Use

You:    "We had a group dinner for ₩65,000. I paid. Split equally."
Claude: Done! Added "Group dinner" for ₩65,000.00 (KRW), split equally
        among 4 members. Each person owes ₩16,250.

You:    "What does everyone owe in the trip group?"
Claude: Here are the current balances:
        • Raj owes you ₩32,500
        • Priya owes you ₩16,250
        • Sam is owed ₩8,000 by the group

You:    "Record that Raj paid me back ₩30,000."
Claude: Payment of ₩30,000 recorded. Raj's balance updated.

You:    "Wait, that dinner was actually ₩72,000. Can you fix it?"
Claude: Updated! "Group dinner" changed to ₩72,000. Shares recalculated.

Works with any currency Splitwise supports — USD, EUR, INR, KRW, JPY, and more.

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How It Works (The Simple Version)

You talk to Claude
       ↓
Claude understands what you want
       ↓
Claude calls this MCP server
       ↓
This server calls the Splitwise API
       ↓
Your Splitwise account updates instantly
       ↓
Everyone's app reflects the change

MCP (Model Context Protocol) is a standard way to give Claude access to external tools. This project is the "Splitwise tool" — a bridge between Claude and your Splitwise account.

See architecture.md for a detailed diagram of how everything connects.

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What You Can Do

Ask Claude	What Happens
"List my groups"	Shows all your Splitwise groups with members
"Who owes what in the [group]?"	Shows all balances
"Add a $52 lunch, I paid, split equally"	Creates the expense
"Add $240 hotel — I paid $120, Alex $80, Sam $40"	Exact split
"Split the $35 cab 50/30/20"	Percentage split
"Record that Alex paid me back $20"	Settlement payment
"Delete that last expense"	Removes it
"Change the dinner to $60"	Updates and recalculates

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Setup

What You'll Need

• Python 3.10+ (python3 --version to check)
• A Splitwise account + API key from secure.splitwise.com/apps
• Claude Desktop or Claude Code

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Step 1: Clone and install

git clone https://github.com/yourusername/splitwise-mcp.git
cd splitwise-mcp
python3 -m venv venv
source venv/bin/activate
pip install -r requirements.txt

Step 2: Add your API key

Create a file called .env in the project folder:

SPLITWISE_API_KEY=paste_your_key_here

Where to get your key:

1. Go to secure.splitwise.com/apps
2. Click "Register your application"
3. Fill in any name (e.g., "My MCP Server")
4. Copy the API Key into your .env file

Step 3: Connect to Claude Desktop

Edit ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "splitwise": {
      "command": "/full/path/to/venv/bin/python3",
      "args": ["/full/path/to/splitwise_server.py"]
    }
  }
}

Restart Claude Desktop. You'll see a hammer icon — that means tools are connected.

Step 4 (Optional): Host on a Server for 24/7 Access

Want it running even when your laptop is off? Deploy to any VPS (I use Hostinger).

See DEPLOY.md for the full step-by-step guide.

Once hosted, connect Claude Desktop via:

{
  "mcpServers": {
    "splitwise": {
      "command": "npx",
      "args": ["-y", "mcp-remote", "http://YOUR_SERVER_IP:8000/mcp", "--allow-http"]
    }
  }
}

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All Available Tools

Tool	What It Does
get_current_user	Your Splitwise profile
list_currencies	All currencies Splitwise supports
list_groups	All your groups with member IDs
get_group	Group details — members, balances, debts
list_expenses	Recent expenses in a group
get_expense	Full details of one expense
create_expense	Add expense (equal, exact, or percentage split)
update_expense	Edit description, cost, currency, or date
delete_expense	Remove an expense
create_payment	Record a settlement between two people

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Troubleshooting

Problem	Fix
Claude doesn't see Splitwise tools	Restart Claude Desktop after editing the config
401 Unauthorized error	Check your API key in .env is correct
"No module named mcp"	Activate your venv: source venv/bin/activate
Server disconnected	Check server is running: sudo systemctl status splitwise-mcp
Wrong paths in config	Use full absolute paths, not relative ones

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Project Structure

splitwise-mcp/
├── splitwise_server.py   ← The entire server (~500 lines, one file)
├── .env                  ← Your API key (never committed to git)
├── requirements.txt      ← Python dependencies
├── architecture.md       ← How everything connects
├── DEPLOY.md             ← How to host on a VPS
└── README.md             ← This file

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Built With

• FastMCP — Python MCP framework
• Splitwise REST API v3
• httpx — HTTP client
• Hosted on Hostinger VPS (Ubuntu)

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Built by a first-time Python developer who just wanted to stop manually logging trip expenses. If I can build it, you can use it.

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License

MIT — use it however you like.