Numeratica — financial planning calculations

@numeratica/mcp

A thin MCP bridge that connects any MCP client (Claude Desktop, Cursor, …) to the Numeratica financial-planning API — retirement Monte Carlo, taxes, RMDs, Social Security, Roth conversions, and more.

Get a free key at https://docs.numeratica.com.

How it works

This package is a transport bridge, nothing more. It reads JSON-RPC from stdin and forwards each message to the hosted POST /mcp endpoint with your API key as a bearer token, then writes the response back to stdout. The tool list and all results come straight from the API — so the bridge always stays in sync and ships no calculation logic of its own. Your key is sent only in the Authorization header and is never logged.

• Zero runtime dependencies (Node ≥ 20 built-in fetch + node:readline).
• Open source (MIT). The interesting part is the API; this is just the wire.

Install

No install needed — your MCP client runs it on demand with npx. (You can also npm i -g @numeratica/mcp to get the numeratica-mcp command.)

Step 1 — look around, no key needed

Start here. This config needs no signup and no key:

{
  "mcpServers": {
    "numeratica": {
      "command": "npx",
      "args": ["-y", "@numeratica/mcp"]
    }
  }
}

Put it in claude_desktop_config.json (Claude Desktop: Settings → Developer → Edit Config) or ~/.cursor/mcp.json (Cursor, or a project .cursor/mcp.json), then restart the client. All 76 tools appear, and you can ask what's available — "What Numeratica tools do you have?"

Without a key the bridge runs in discovery-only mode: browsing the catalogue works, running a calculation returns a message telling you to add a key. That's the intended state, not a failure.

Step 2 — add a key to run calculations

Get a free key at docs.numeratica.com/get-key, then add one line:

{
  "mcpServers": {
    "numeratica": {
      "command": "npx",
      "args": ["-y", "@numeratica/mcp"],
      "env": { "NUMERATICA_API_KEY": "nmr_sk_your_key_here" }
    }
  }
}

Restart, and the tools are live. Try: "Run a retirement Monte Carlo for a 40-year-old retiring at 65."

Configuration

Variable	Required	Default	Notes
NUMERATICA_API_KEY	to run calculations	—	Your key. Get one free at docs.numeratica.com/get-key. Never logged. Omit it to browse the catalogue in discovery-only mode.
NUMERATICA_BASE_URL	no	https://api.numeratica.com	Override the API base (e.g. for testing).

You can also pass the key with --key <value> or --key=<value> instead of the env var, but prefer NUMERATICA_API_KEY: a key on the command line is visible to ps for every user on the machine, lands in shell history, and is stored verbatim in MCP client config files that people routinely paste into issue reports. For a non-env option that avoids all three, use --key-file <path>.

Links

• API docs & reference: https://docs.numeratica.com
• Get a free key: https://docs.numeratica.com/get-key

License

MIT © Numeratica / Francis Townsend-Merino