Monarch for Claude

This is a local, single-user Windows connector for Claude Desktop. It exposes the exact tool inventory described in src/tools/contracts.ts: read-only account/transaction/category/tag/rule tools plus an audited, preview-and-confirm path for classification rules.

Rule management supports create, update, delete, and reorder; merchant/original-statement, account, category, and amount criteria; category, tag, merchant-name, report-visibility, and review-status actions; and an explicit apply_to_existing_transactions option for create/update previews. Historical application is never implicit: the preview scans the full available transaction history, reports the matching count and examples, and the apply step still requires local confirmation.

Individual transaction management supports previewed updates to merchant/payee name, category, notes, reviewed state, report visibility, and the complete tag set. Every update is single-use, checks that the transaction has not changed since preview, requires local confirmation, performs one fixed non-retried mutation, and verifies the result. Transaction deletion is not implemented or allowlisted.

For historical application, the canonical preview shape is {"kind":"create","rule":{...},"apply_to_existing_transactions":true}. The flag belongs at the top level alongside kind and rule. For compatibility, apply_to_historical and applyToExistingTransactions are also accepted either there or inside rule; the server normalizes them before validation. Invalid rule requests return INVALID_INPUT with safe field paths and validation messages instead of an opaque error.

Install

Download the .mcpb file from the latest GitHub release, verify it against the accompanying .sha256 file, and install it using Claude Desktop's Extensions UI.

Related MCP server: Tiller Money MCP Server

Build

npm ci
npm run ci

The resulting bundle and SHA-256 file are in dist/. No Node installation should be needed at runtime because Claude Desktop supplies Node.

Connect and reauthenticate

Call connect_monarch in Claude. It opens a dedicated browser profile; sign in directly with Monarch. No password, token, cookie, or OTP is accepted by an MCP tool. get_monarch_connection_status reports safe diagnostic codes only. Expired sessions are removed and require reconnecting.

Uninstall

Remove the extension in Claude Desktop. If desired, separately delete %LOCALAPPDATA%\MonarchForClaude\auth.bin and %LOCALAPPDATA%\MonarchForClaude\logs to remove encrypted local session data and diagnostics.

Authentication diagnostics

Sanitized authentication events are returned by get_monarch_connection_status in diagnostic_trace. A best-effort file copy is also written inside the extension runtime at %LOCALAPPDATA%\MonarchForClaude\logs\authentication.log and rotated at 1 MiB, but Claude Desktop's isolation may make that path inaccessible from the host. Every file entry carries a timestamp and the extension version. Diagnostics contain stages (browser discovery and launch, DevTools attachment, cookie and request observation, session save, verification, cleanup), safe error codes, PowerShell exit codes and a fixed error class for DPAPI failures, Monarch API host/path and HTTP status codes, header names, header-presence booleans, and cookie names, domain, path and flags only. If the log file cannot be written, get_monarch_connection_status reports AUTH_LOG_FILE_WRITE_FAILED with the error code. They never record passwords, OTPs, authorization tokens, cookie values, CSRF values, GraphQL response data, or financial data.

Live testing

Live tests are intentionally absent from the default commands. Before use with a real account, validate the browser capture with the owner present and use an impossible, generated merchant criterion for rule write acceptance tests. Never commit real data or credentials.

This is an independent community project and is not affiliated with or endorsed by Monarch Money or Anthropic.