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Jacobian MCP Server

local only

Jacobian runs on your own machine — the client starts it, so there is no endpoint to ping. 249 installs a week from npm. Last commit 29 Oct 2026.

Executable mathematics and independent verification for AI agents.

Installs per day peak 190 · avg 47 · +234% w/w
a month agotoday
249
Installs / week
npm · jacobian
351
Stars
88 open issues
29 Oct 2026
Last commit
14 releases in 90 days
MIT
License
Python

What the code does

We read the source, 4 d ago · rules 995398eba69f

Capabilities

What this server is able to do. For an MCP server this is often the job itself — a terminal server runs commands because that is what it is for. Listed so you know what you are plugging in, not as an accusation.

  const child = spawn(
In the project's build, not in the package

Found in continuous integration, deployment or infrastructure files, or in a neighbouring package of the same monorepo. None of this is installed when you add the server: it describes how the project is built and released. We list it because a leaked key in a build pipeline is still a real problem, but it is not something this server does on your machine.

        subprocess.run(
Dumps the whole environment tools/pytest_lifecycle.py:148
            environment=dict(os.environ),

Is this your server and something here is wrong? Tell us — corrections are free and do not require a plan.

This code can reach further than it looks

We found places where it runs commands, builds paths or queries from values it is given. None of that is a flaw by itself — it becomes one when the code changes, and code changes quietly between releases. We re-read it on every one.

Three servers free · no card

Connect this server

This server runs on your own machine — install it with the package manager and the client starts it for you. Package name taken from the official registry entry.

run in your terminal
claude mcp add jacobian -- npx -y jacobian
~/Library/Application Support/Claude/claude_desktop_config.json
{
  "mcpServers": {
    "jacobian": {
      "command": "npx",
      "args": [
        "-y",
        "jacobian"
      ]
    }
  }
}
~/.codex/config.toml
[mcp_servers.jacobian]
command = "npx"
args = ["-y", "jacobian"]
.cursor/mcp.json
{
  "mcpServers": {
    "jacobian": {
      "command": "npx",
      "args": [
        "-y",
        "jacobian"
      ]
    }
  }
}
.vscode/mcp.json
{
  "servers": {
    "jacobian": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "jacobian"
      ]
    }
  }
}

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Jacobian — questions

Answers built from our own checks of this server.

Why is there no uptime for Jacobian?
Jacobian runs on your own machine over stdio — there is no network address to reach, so uptime cannot be measured for it by anyone. What can be measured is adoption: the npm package jacobian was installed 249 times last week.
How do I connect Jacobian?
Copy the ready config from this page. We generate it for Claude Code, Claude Desktop, Codex, Cursor and VS Code, each in the form that client actually reads. It runs locally, so the command pulls jacobian straight from npm; nothing to host, nothing to sign up for.
How many people use Jacobian?
The npm package jacobian was installed 249 times in the last week. Week over week that is +234%. We show installs rather than GitHub stars on purpose: a star is a bookmark, an install is someone actually running it.
Is Jacobian open source?
Yes — it is published under the MIT licence, written in Python, 351 stars on GitHub and 88 open issues. The source link is on this page, so you can read exactly what it does with your data before you connect it.