Sem

About

Sem is a semantic version control tool that sits on top of Git. It parses code with tree-sitter, extracts functions, classes and methods as entities, and reports which entities changed instead of which lines. Through MCP, agents get the same verbs as the command line: find entities, list callers and references, run impact analysis, check a change, and produce review certificates.

It runs locally over stdio from the @ataraxy-labs/sem npm package, or from the sem binary with the mcp subcommand. It works in any Git repository with no setup and needs no API key. Cloud-backed queries are optional and opt-in per repository.

What you can do

• Find functions, classes and methods by name
• List callers and references of an entity
• Run impact analysis and find affected tests
• Diff at entity level instead of by line
• Check a change with the project's own compiler, linter and tests
• Generate a review certificate for a commit range
• View entity history and last-changed blame

Tools

Local servers list their tools once they’re running, and this one doesn’t publish its list in advance. Your client shows them after you add it.

Example prompts

• Which functions changed between main and HEAD in this repo?

• Find who calls parse_config and which tests it affects.

• Run a semantic check on my uncommitted changes.

• Generate a review certificate for main..HEAD.

Set up

Every client starts Sem on your machine with the same command. Pick yours; the page remembers your choice.

claude mcp add --transport stdio sem -- npx -y @ataraxy-labs/sem

{
  "mcpServers": {
    "sem": {
      "command": "npx",
      "args": [
        "-y",
        "@ataraxy-labs/sem"
      ]
    }
  }
}

{
  "mcpServers": {
    "sem": {
      "command": "npx",
      "args": [
        "-y",
        "@ataraxy-labs/sem"
      ]
    }
  }
}

code --add-mcp '{"name":"sem","type":"stdio","command":"npx","args":["-y","@ataraxy-labs/sem"]}'

{
  "servers": {
    "sem": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "@ataraxy-labs/sem"
      ]
    }
  }
}

{
  "mcpServers": {
    "sem": {
      "command": "npx",
      "args": [
        "-y",
        "@ataraxy-labs/sem"
      ]
    }
  }
}

codex mcp add sem -- npx -y @ataraxy-labs/sem

[mcp_servers.sem]
command = "npx"
args = ["-y", "@ataraxy-labs/sem"]

gemini mcp add sem npx -- -y @ataraxy-labs/sem

{
  "mcpServers": {
    "sem": {
      "command": "npx",
      "args": [
        "-y",
        "@ataraxy-labs/sem"
      ]
    }
  }
}

Embed

Show Sem in a README or on your site. Each embed links to this page, uses the server’s own install command, and sets no cookies. How embeds work

The card, the iframe and the JSON are in English. Add ?lang=it, fr, de or es to their address for another language.

README badge Website card iframe JSON AI prompt

README badge

Markdown

[![Sem on mcp.tc](https://mcp.tc/i/sem/badge.svg)](https://mcp.tc/i/sem)

HTML

<a href="https://mcp.tc/i/sem"><img src="https://mcp.tc/i/sem/badge.svg" alt="Sem on mcp.tc" height="20"></a>

It follows the reader’s light or dark mode. Add ?theme=light or ?theme=dark to fix it, or ?style=compact to show the mark without the word.

Website card

HTML

<script src="https://mcp.tc/w/sem.js" async></script>

The card appears where the tag is. Add data-theme="dark" or data-size="compact" to the tag to change it. The file holds everything it needs, so it makes no other requests and sets no cookies.

iframe

HTML

<iframe src="https://mcp.tc/embed/sem" title="Sem on mcp.tc" width="420" height="200" loading="lazy" allow="clipboard-write" style="border:0;border-radius:8px;max-width:100%"></iframe>

Use it on pages that don’t allow scripts. Add ?theme=light or ?theme=dark to the address to fix the colors.

JSON

The listing as data for your own pages and tools: name, tagline, install command, tools and the “Add to” links. Any site can read it (CORS is open).

https://mcp.tc/i/sem.json

What each field means

AI prompt

Paste this into an AI coding assistant, such as Claude Code or Cursor, and it adds the Sem card to your site.

Markdown

Add the mcp.tc card for Sem, an MCP server, to my website. It is one static script: no build step, no package to install, no cookies.

Put this tag where the card should appear. The card renders right before it:

```html
<script src="https://mcp.tc/w/sem.js" async></script>
```

To show the card somewhere else, put this placeholder there and load the same script once, for example before `</body>`. Keep the link inside: visitors without JavaScript see it.

```html
<div data-mcptc="sem"><a href="https://mcp.tc/i/sem">Sem on mcp.tc</a></div>
```

Options:
- `data-theme="light"` or `"dark"` on the tag or the placeholder fixes the colors. Without it, the card follows the visitor’s light or dark mode.
- `data-size="compact"` gives a smaller card without the tagline.
- The CSS variable `--mcptc-max-width` on the placeholder or a parent sets the width (default `520px`).
- `?lang=` on the script URL sets the card’s language: `en`, `it`, `fr`, `de` or `es`.

If the site has a Content Security Policy, allow `script-src https://mcp.tc` and `img-src data:` (the icon is inline).

For a README or other Markdown docs, use the badge instead:

```markdown
[![Sem on mcp.tc](https://mcp.tc/i/sem/badge.svg)](https://mcp.tc/i/sem)
```

Reference: https://mcp.tc/embed

Change history

This server runs on your computer, so we follow its npm package: each new version shows up here, with edits by its owner.

1. 6 Oct 2026, 21:22 UTC, Automatic check

   Tracking started: version 0.27.0.

FAQ