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splitwise-mcp

MCP server that exposes every endpoint from Splitwise's public self-serve API docs as MCP tools.

Current coverage from spec/paths/index.yaml: 27 API operations.

Authentication

Splitwise uses Bearer authentication for API calls. This server accepts any of these env vars:

• SPLITWISE_API_KEY (recommended for personal use; easiest path)
• SPLITWISE_ACCESS_TOKEN
• SPLITWISE_OAUTH_ACCESS_TOKEN
• SPLITWISE_BEARER_TOKEN

If none are set, tool calls fail with an auth error.

Which key/credential do you need?

• Personal scripts/single account: create a Splitwise app and use its personal API key as a Bearer token.
• Multi-user app: use OAuth 2.0 Authorization Code (client key + client secret) to get user access tokens, then pass the access token as Bearer.
• OAuth 1.0 is not used by the current docs.

Run with Bunx

Bunx expects a package + executable. For path/GitHub sources, use -p and then the bin name (splitwise-mcp).

Published package (npm):

SPLITWISE_API_KEY=your_token bunx splitwise-mcp

Local path source:

SPLITWISE_API_KEY=your_token bunx -p /absolute/path/to/splitwise-mcp splitwise-mcp

GitHub source:

SPLITWISE_API_KEY=your_token bunx -p github:adinschmidt/splitwise-mcp splitwise-mcp

Note: bunx /path/to/repo is not supported by Bun 1.3.x. Use -p form above.

MCP Client Config Example

Using published npm package:

{
  "mcpServers": {
    "splitwise": {
      "command": "bunx",
      "args": ["splitwise-mcp"],
      "env": {
        "SPLITWISE_API_KEY": "your_splitwise_token"
      }
    }
  }
}

Using a local checkout:

{
  "mcpServers": {
    "splitwise": {
      "command": "bunx",
      "args": ["-p", "/absolute/path/to/splitwise-mcp", "splitwise-mcp"],
      "env": {
        "SPLITWISE_API_KEY": "your_splitwise_token"
      }
    }
  }
}

Tool Naming

Each API path is mapped to one tool name by path normalization.

Examples:

• /get_current_user -> get_current_user
• /get_user/{id} -> get_user_id
• /delete_expense/{id} -> delete_expense_id

There is also a helper tool:

• splitwise_list_operations: lists all registered Splitwise operations.

Request Shape for Tools

Every tool accepts:

• Path/query parameters as top-level fields (for example id, limit, offset)
• body for JSON request bodies (when the endpoint supports/needs a body)
• For best results, pass body as an object. If you pass a string, use a JSON object string or URL-encoded form string.

Spec Sync

To refresh specs from Splitwise official docs repo:

bun run sync-spec

Then restart the MCP server.

Sources

• Splitwise API docs: https://dev.splitwise.com/
• Splitwise API OpenAPI source: https://github.com/splitwise/api-docs