Agents can set up a plan. Your browser runs it.

{
  "mcpServers": {
    "firecalc": {
      "command": "node",
      "args": ["/ABSOLUTE/PATH/RetirementCalc/mcp/server.mjs"]
    }
  }
}

There is no public compute API. The local MCP stays on your computer. The draft hosted MCP only builds links. A server that returns success rates is not offered.

The same keys are what the in-app Share button writes. firecalc-io.js builds and reads them without the page.

• Stagflation squeezeVillain years 1977–1981 · starts 1977
• Rate wall of ’81Villain year 1981 · starts 1981
• Bond rout of ’94Villain year 1994 · starts 1994
• Dot-com hangoverVillain years 2000–2002 · starts 2000
• GFC crashVillain year 2008 · starts 2008
• 2022 rate shockVillain year 2022 · starts 2022, 3 years max

A pack runs for the plan’s length, never past 2024. There is no pack for 1966 or 1973–74, which are before the table. There is also none for Black Monday or the COVID crash, because 1987 and 2020 were up years in annual data. Agents can add pack=<id> to a retirement share link to open that pack with the plan’s numbers.

1. Ask firstAsk which calculator, the return path (shuffled years or historical cycles), the stock mix, taxes, and whether Social Security is on. Do not invent a 7% return.
2. Build the linkBuild a https://firecalc.ai/ URL with the share keys. Do not send the numbers anywhere to compute a result. The draft hosted MCP only writes the link.
3. Disclose the sampleSay the sample is US large-cap stocks and 10-year Treasuries from 1975 through 2024. It does not include 1966 or 1973–74. This is an illustration, not advice.
4. Hand offSend the person here for charts, the path table, and editing. Chat is a poor place to scrub a plan.

• Years to a savings goalLiveOn the calculator. Goal is today’s purchasing power. Contributions are income minus spending, and never below zero.
• Retirement survivalLiveOn the calculator. Success means the portfolio is above zero at the end of every year of the horizon.
• Share linkLiveOn the calculator. firecalc-io.js encodes and decodes the same query keys.
• Spending or stock-mix stressChart onlyA chart after you run retirement or savings. Not a separate tool.
• Social Security claimingInput onlyAn input (62–70), off unless you turn it on. No side-by-side 62 vs 70 tool.
• Coast, barista, sabbaticalGuide onlyNo coast solver and no barista switch. The Coast FIRE guide shows the zero-contribution check: income equal to spending, and real raises at 0% so saving does not resume.
• Named historical stress packsLiveOn the retirement results. Six named stretches inside 1975–2024, each with its exact years and a share card drawn in the browser. See the pack list.
• Local MCPLiveIn the repository as mcp/server.mjs. Stdio on your machine, same engine as the site. Not a server FIREcalc hosts. See the Local MCP card.
• Hosted link-only MCPDraftDeveloper Mode URL: https://firecalc-link-mcp.aye-dreee-an.workers.dev/mcp. Not in the app directory. Builds share URLs. No trial math. See the Hosted MCP card.
• Chat plugin and skillsNot publishedNot in the ChatGPT directory. A Custom GPT can still follow the link-only rules. Skills are not a download.

• llms.txtShort index for agents
• llms-full.txtFull methodology
• agents.txtNo hosted agent API, no payment
• agents.jsonMachine-readable statement