MCP server: the Roth Conversion Calculator inside your AI assistant

What it does

This server gives an AI assistant the same optimizer that runs in the Roth Conversion Calculator. Given your age, your traditional, Roth and brokerage balances, your spending and your Social Security, it solves a linear program over the US federal tax brackets and returns how much to convert to Roth in each year, the tax on it, where the spending comes from, and the ending balances. It also solves the same plan with no conversions at all, so you can see what converting is worth. IRMAA (the Medicare surcharge), the 3.8% NIIT and real state brackets are available as advanced options, off by default just like the web tool. An assistant doing this arithmetic by itself will guess; here a solver does it.

Still working and wondering how to split your savings between Roth and traditional? That is the Roth vs Traditional Calculator, which has its own server.

How to connect

Claude: at https://claude.ai/customize/connectors, add a custom connector with the URL above. No OAuth needed.

Claude Code: claude mcp add --transport http roth-conversion https://roth-conversion-calculator.kindoflost.com/mcp

Other assistants and clients: anything that accepts a remote MCP server over HTTP; use the same URL.

Tools

Three tools, all read-only: none of them changes anything or stores your numbers.

get_conversion_example

Return a complete example input for optimize_roth_conversions with a one-line explanation of every field. No solve. Edit it to the user's situation. kind 'single' (default: a 60-year-old early retiree with a traditional IRA, a brokerage account and Social Security later) or 'married'.

Inputs (* = required):

Returns: A complete example input object (single or married), a one-line explanation of every field (field_notes), the required fields and the next step. Nothing is solved.

optimize_roth_conversions

Find the best Roth conversion amount for each year of a retirement plan, with living expenses funded from the right accounts and tax paid each year. Returns per-year conversions, taxes and balances, the after-tax wealth at the end with vs without conversions, totals, a plain-language plan narrative and the assumptions used. Advanced options (IRMAA, NIIT, real state brackets) are off by default. Runs in 1-3 seconds (up to ~15 with IRMAA/NIIT on a long horizon). All money in today's dollars. Optimal for the stated assumptions; not tax advice. Call get_conversion_example first if unsure of the shape.

Inputs (* = required):

Returns: A short plain-text summary plus structured data: the conversion amount for every year (conversion_schedule), a year-by-year table (conversion, income tax, marginal rate, withdrawals from each account, start-of-year balances), the after-tax wealth at the end of the plan with the optimal conversions against the same plan with none, total tax, ending balances, a plain-language plan narrative, the assumptions used (defaults included) and the disclaimer.

check_request

Say in plain words what the user wants (e.g. 'I'm still working and want to know Roth vs traditional 401k'). Returns whether this optimizer can do it and, if not, the closest thing it can do (or the sister server that can). Fast, no solve.

Inputs (* = required):

Returns: Whether the request fits (supported), the unsupported parts with the closest thing the server can do (or the sister server that can), and what the server does.

Example

Prompt:

I'm 60, single and retired. I have $900,000 in a traditional IRA, $60,000 in a Roth IRA and $350,000 in a brokerage account (about $120,000 of it is long-term gain). I spend about $60,000 a year, and I expect $36,000 a year of Social Security from 70. Assume a 5% real return and plan to age 92. How much should I convert to Roth each year, and what does it add compared with not converting?

The assistant calls get_conversion_example, fills in your numbers and calls optimize_roth_conversions. The text the tool returns for that example (generated live from the server):

Optimal for these assumptions (age 60, single, plan to 92).
Convert to Roth, by age: 60: $90,014, 61: $66,500, 62: $66,500, 63: $28,127, 64: $700, 65: $2,750, 66: $2,750, 67: $2,750, 68: $2,750, 69: $2,750. Total $265,591 over ages 60-69.
After-tax wealth at 92 (today's dollars): with conversions $896,838; with none $818,935 (conversions add +9.5%, $77,903).
Income tax over the plan: $264,738 with conversions, $269,601 without. Ending balances at 92: traditional $0, Roth $896,838, brokerage $0.
Assumes 5% real return, 24% tax on leftover traditional money, state: none (0%), IRMAA off, NIIT off.
Note: Nothing is left in the traditional IRA
Note: Your conversion window is ages 60–63
Note: It stops at the 22% bracket
Optimal for these assumptions only; not tax advice. Results depend on the assumed real return, the future tax rate and current tax law.
See every year and adjust inputs: https://roth-conversion-calculator.kindoflost.com

And the start of the structured data, trimmed:

{
  "status": "ok",
  "optimal_for_these_assumptions": true,
  "summary": {
    "metric": "after_tax_terminal_wealth (today's dollars, at age 92)",
    "with_optimal_conversions": 896838,
    "with_no_conversions": 818935,
    "conversions_add": {
      "dollars": 77903,
      "pct": 9.5
    },
    "total_converted_to_roth": 265591,
    "conversion_ages": "60-69",
    "total_income_tax_with_conversions": 264738,
    "total_income_tax_without_conversions": 269601,
    "of_which_state_tax": 0,
    "niit_paid": 0,
    "irmaa_surcharges_paid": 0
  },
  "conversion_schedule": [
    {
      "age": 60,
      "amount": 90014
    },
    {
      "age": 61,
      "amount": 66500
    },
    {
      "age": 62,
      "amount": 66500
    },
    {
      "age": 63,
      "amount": 28127
    },
    {
      "...": "more years"
    }
  ],
  "...": "plan_by_year, end_of_plan, plan_notes, assumptions, note"
}

Limits

• Ages 18 to 90; plan horizon up to 70 years (end age up to 110); balances up to $1,000,000,000.
• One household: single, or married filing jointly with both spouses assumed the same age and both alive for the whole plan. 2026 US federal tax; a US state's brackets or a flat state rate. One fixed real return, no random market paths. ACA premium-credit modeling is in the web version's advanced options but not on this server.
• One solve runs at a time; a run takes a second or two (a few seconds more with IRMAA or NIIT on, each solve capped at 5 seconds). If the server is busy the assistant is told to retry in about 20 seconds.
• Rate limit: 20 solves per network address per 10 minutes. Requests larger than 1 MB are refused.

Honest note

The plan is optimal for the stated assumptions (the real return, the future tax rate, current tax law and the other inputs), not for the future. Change the return or the tax rate on what is left and the answer can change. “Without conversions” is the same model with every conversion forced to zero. This is not tax advice, and I'm not a CPA: use the result as a starting point to bring to one. Money is in today's dollars.

Try it yourself

Prefer a form with charts and every year laid out? Use the calculator. Details on what is stored are in the privacy policy.

Support: mario@kindoflost.com.