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MCP Tax Calculator in Claude Desktop

2026 US federal brackets, computed in the conversation. us_federal_tax applies the 2026 US federal brackets for a single filer — marginal rates by band with the standard deduction applied first — and returns tax owed plus the effective rate; it is a planning estimate computed exactly, not a filing tool, and the bracket table it uses is in the source where you can read it.

Tax questions start as hallway math; with the 2026 brackets loaded the estimate comes back with the effective rate, in the chat, before the search result would have loaded its cookie banner.

What you get in Claude Desktop

You say	Tool
Federal tax on 95,000 gross, single filer, 2026 brackets.	`us_federal_tax`
What if I gross 160,000?	`us_federal_tax`
Compare effective rates at 60k and 120k.	`us_federal_tax, twice`

The contract suite walks real stdio cases through the bracket table: 95,000 gross less the 15,750 standard deduction is taxed band by band with the marginal rate applied only above each threshold, the returned effective rate equals tax divided by gross, and a below-deduction income returns zero.

Install it in Claude Desktop

The file is claude_desktop_config.json, and the key inside it is mcpServers.

Scope	Path
macOS	`~/Library/Application Support/Claude/claude_desktop_config.json`
Windows	`%APPDATA%\Claude\claude_desktop_config.json`

One click, with no JSON. Download tax-calc.mcpb from the latest release and open it. Claude Desktop installs it as an extension and runs it on the Node runtime it ships with, so neither your PATH nor your node version comes into it, and there is no file to edit. Everything below is the manual route, for when you want the entry in the config file itself.

The config block, which needs both strings absolute:

{
  "mcpServers": {
    "tax-calc": {
      "command": "node",
      "args": ["/absolute/path/to/mcp-servers/servers/tax-calc/dist/index.js"]
    }
  }
}

If node came from nvm, asdf or homebrew, use the absolute path that which node prints rather than the bare word, because a stdio server started by this app inherits a limited PATH:

"command": "/Users/you/.nvm/versions/node/v22.14.0/bin/node"

The node command above wants a built file. From a clone, once:

git clone https://github.com/theluckystrike/mcp-servers.git
cd mcp-servers && npm install
npm run build -w packages/mcp-license -w servers/tax-calc

That writes servers/tax-calc/dist/index.js, and its absolute path is the one argument the config needs.

The npm packages are not published yet, so the form below returns a 404 today. It is here because it is what the entry becomes the day the publish lands, with nothing else changed:

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

Save, then completely quit Claude Desktop and start it again. A window reload is not enough.

Nothing is published to npm yet, so the working install paths are the ones above: the .mcpb bundle from the latest release, a clone and build, or the hosted URL.

No install: the hosted endpoint

There is no hosted endpoint for this one yet. MCP Tax Calculator runs locally over stdio with the config above, which is also the only form in which it reads and writes files on your own disk. Thirty of the servers in this collection are served at https://mcp.zovo.one/mcp/<name> over MCP streamable HTTP; https://mcp.zovo.one/mcp/connect lists them and prints a ready URL for each.

Claude Desktop notes worth knowing first

Two documented facts decide whether the entry works: every path in claude_desktop_config.json must be absolute, and a stdio server started here inherits only a limited, platform-dependent subset of environment variables. If node came from nvm or homebrew, paste what `which node` prints instead of the bare word. The .mcpb route avoids both: Claude Desktop ships a built-in Node.js environment.

Free: Everything: one tool, no metering, no key. Pro is $19 once, verified offline.

Questions

Where is claude_desktop_config.json?

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json. Windows: %APPDATA%\Claude\claude_desktop_config.json. There is no published Linux path. Settings, Developer, Edit Config opens the right copy and creates it if it does not exist.

I added it and MCP Tax Calculator does not appear.

In order: did you fully quit and restart, not just close the window? Is every path absolute? And is the command resolvable, given the limited environment a stdio server inherits here? If node came from nvm, paste what which node prints.

Can I install it without editing JSON?

Yes. An .mcpb bundle, the format renamed from .dxt, opens with Claude and shows an installation dialog. One you built yourself goes in through Settings, Extensions, Advanced settings, Install Extension.

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