Why FinPlan?¶
AI assistants are great at conversation, but financial planning needs exact math. When you ask "Can I retire at 60?", the answer depends on tax brackets, contribution limits, investment returns, and dozens of interconnected rules. FinPlan gives your AI assistant a real calculation engine so it can answer with numbers instead of narratives.
The problem with asking AI about money¶
Large language models generate plausible-sounding text. That's the wrong tool for financial math. Worse, without a dedicated engine, an LLM will reinvent the wheel every session — writing the same tax logic, the same projection math, the same account rules from scratch each time, with no guarantee it got any of it right. FinPlan writes that code once, tests it, and optimizes it so the LLM doesn't have to.
| What you ask | What an LLM alone does | What FinPlan does |
|---|---|---|
| "How much tax will I owe?" | Estimates from training data, often wrong | Looks up the actual IRS brackets for your filing status and year |
| "Can I max out my 401(k)?" | Cites a limit that may be outdated | Uses the current IRS contribution limit for your age |
| "Will I have enough to retire?" | Gives a vague, hedged paragraph | Runs a Monte Carlo simulation across thousands of market scenarios |
Every answer from FinPlan is computed, not generated. No hallucinations, no made-up numbers, no confident-sounding guesses.
Deterministic, not probabilistic¶
The same inputs always produce the same outputs. Run a projection today, run it again tomorrow with the same data — you get identical results. This matters when you're making real financial decisions:
- Reproducible results — Share your profile with a spouse, advisor, or future self and get the same numbers every time.
- Auditable calculations — Every tax bracket, contribution limit, and deduction comes from published IRS tables. Nothing is estimated or interpolated.
- Version-controlled rules — Tax law changes yearly. FinPlan's modular tax engine is updated to match, with clear boundaries between tax years.
Fast and private¶
FinPlan comes in two flavors: a local CLI you install on your machine, and a remote MCP server you can connect to without installing anything. Either way, your personally identifiable information stays on your machine — FinPlan doesn't retain or store any of your financial details.
- Sub-second calculations — Projections that would take an LLM paragraphs of hedged reasoning are computed in milliseconds.
- Closed-form math by default — FinPlan uses analytical solutions for speed. Want to see the full range of outcomes? Switch to Monte Carlo mode for 1,000+ scenario simulations — it takes longer, but shows variation better.
- You pick the deployment — Use the local CLI for fully offline, zero-dependency operation, or connect to the remote MCP server for instant setup with no installation. Your PII stays local either way.
Tested and documented¶
FinPlan's calculation engine is backed by an extensive test suite. Every tax bracket, every account type, every edge case is covered by automated tests that run on every change.
- Hundreds of unit tests — Core financial logic is tested against known-correct values, not spot-checked by hand.
- Real IRS data — Tax tables are validated against published IRS documents, not scraped from blog posts.
- Structured tool documentation — Every MCP tool has a defined schema with typed inputs and outputs. Your AI assistant knows exactly what parameters to pass and what to expect back — no guessing, no prompt engineering tricks.
Why a CLI and MCP server?¶
Most financial tools give you a web dashboard. FinPlan gives your AI assistant a set of structured tools it can call programmatically. Here's why that's better when you're working with an AI agent:
Structured I/O eliminates hallucination¶
MCP tools accept typed JSON inputs and return typed JSON outputs. The AI doesn't need to scrape a webpage, parse a PDF, or interpret a screenshot. It calls a function with exact parameters and gets exact results. There's nothing to misread or make up.
The AI stays in control¶
Instead of you clicking through tabs and menus, your AI assistant orchestrates the entire workflow: load your profile, update an account balance, run a projection, compare scenarios — all in a single conversation. You describe what you want in plain language; the tools handle the math.
Composable by design¶
Each tool does one thing well. Your AI assistant can chain them together in ways a fixed dashboard can't:
- "What happens if I max out my HSA and switch to a Roth 401(k)?" — Run both changes, project, compare.
- "Show me retirement at 60, 62, and 65 side by side" — Three projection calls, one summary.
- "What's my tax situation if we file jointly vs. separately?" — Two tax calculations, direct comparison.
A dashboard would need a dedicated feature for each of these. With tools, the AI composes them on the fly.
Your data, your files¶
Everything is saved as plain JSON files on your local machine. No accounts to create, no cloud sync, no terms of service. Back them up however you want. Version them in git. Delete them and start over. You own the files — and because the data is yours, your AI assistant can create custom outputs like charts, visuals, or reports in whatever style you want.
Works with any MCP-compatible agent¶
FinPlan isn't locked to one AI provider. Any assistant that supports the Model Context Protocol — Claude, ChatGPT, or others — can use the same tools. Switch providers without losing your financial data or learning a new interface.
Get started¶
Ready to try it? Connect your AI assistant and run your first projection in minutes.