Expense Organizer

Application-native AI,in production.

Expense Organizer is a shared-expense platform developed and published by Rusmex Software Solutions, and our production reference implementation for application-native AI: Claude operates through the same domain model, permissions, and workflows used by the application itself.

Production use case: divorced parents reconciling shared child-related expenses across households. The FemExpensor mobile app captures receipts; the web application keeps the ledger; Claude and other assistants reach both through MCP.

Fig. A — how Claude reaches the ledger click a layer

Three kinds of client talk to the ledger. The in-app AI agent (Penny), built into the app, runs on Claude through the Anthropic API and works beside you on whatever screen is open, signed in as you. Claude Code, Claude Desktop, claude.ai and any other MCP client connect from outside through the MCP server, also signed in as you. And the app’s own background jobs call a model with nobody watching, to classify and read every document you attach. All three arrive through the same tool layer. None of them has a private door.

Every capability is defined once, in application code, and published as a tool. Seven server tools reach the outside world over MCP, behind OAuth 2.1 with PKCE. Inside the app, each screen publishes its own tools only while it is on screen: an open expense form offers fill and populate, the grid offers filter, sort and status changes, the drafts queue offers promote and merge. The in-app agent’s tool list is assembled fresh for every message from what is actually mounted, and the server tools are projected into it from the same code, with one schema and one description.

A tool calls the same service the button calls. Creating an expense from a receipt opens a pre-filled form that you review and save; a status change runs the same transition rules as the toolbar; a duplicate check is the same query a reviewer gets. Splits between guardians, statuses, permissions and the expense event log live here and nowhere else. The model proposes, the application decides, and you confirm anything that is written or destroyed.

SQL Server holds the truth: expenses and who they were for, the guardians who split them, tags, cycles, and every attached document as a content-addressed artifact carrying its OCR text, its classification and the line items read from it. A line item a person typed is locked and never overwritten by extraction; one a model read is stamped with the hash of the document it came from. Full-text search spans the expense and the receipt text, providing for intelligent search inside the receipts.

AI is a supported client of the application, not a bypass around it. Every call is authenticated, scoped to the signed-in member’s family group, and subject to the same business rules and event log as the web UI. Money math, splits, statuses and permissions stay in application code; the model handles capture, reading, summary and conversation — and when it cannot tell which answer is right, it records nothing rather than guessing.

What is implemented

Claude-powered conversational interaction with application data

Claude API integration inside the product

Application-specific tool calling rather than free-form prompt-only behavior

Authenticated, user-scoped access to household data and actions

MCP server exposing Expense Organizer capabilities to Claude and other compatible assistants

Receipt and document ingestion with AI-assisted extraction and categorization

Business rules, permissions, and auditability enforced by the application

Mobile/web product architecture, not a prototype or static demo

Blazor and .NET web application, SQL Server, native mobile apps. Model-aware but not model-locked: Claude is used where it is part of the implementation; the MCP and tool layer works with other compatible assistants.

Configurable platform

The platform is configurable and can be branded for a business. The infrastructure — domain model, permissions, audit, MCP — is shared across configurations. The platform customized for Divorced Families is live at family.expenseorganizer.com. Events (group weekend outings, weddings) and Rental Properties are future customizations of the same core platform.

Visit ExpenseOrganizer.com

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