# Arc (npm · @hudsonkit/arc-mcp)

Author, validate, lay out, render, and diff architecture diagrams as code.

- Trust score: 87/100 (high trust)
- Change this week: +3
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-11-05

## Components

- npm · `@hudsonkit/arc-mcp`: 87/100 (this document), [markdown](https://verifymcp.io/servers/hudsonkit-arc/hudsonkit-arc-mcp.md), [page](https://verifymcp.io/servers/hudsonkit-arc/hudsonkit-arc-mcp)

## Channel facts

- Registry: `npm`
- Package: `@hudsonkit/arc-mcp`
- Version: `0.14.1`
- Transport: `stdio`

## Trust breakdown

How this component scores in each security and reliability category. Every signal is checked automatically from public evidence about the published package, including repeated runs of it in an isolated sandbox, and we only credit what we can confirm. Scores are 0–100 per category. Scoring method: https://verifymcp.io/docs/scoring (what has changed: https://verifymcp.io/docs/scoring/changelog)

Scored 2026-11-05.

- **Supply Chain Security**: 100/100
  - No malware found by supply-chain analysis.
  - No known CVEs affecting this package version or its production dependencies.
  - No install/post-install scripts declared.
  - No production dependencies, so there is no dependency health to assess.
- **Provenance & Transparency**: 97/100
  - Source repository is publicly reachable at the declared URL.
  - Cryptographically verified build provenance (signed, bound to hudsonkit/arc).
  - Clear OSI-approved license (MIT).
  - Actively maintained (last published 10 days ago).
  - Disclosure check failed: no security disclosure policy was found in the source repository.
- **Schema Quality & AI Usability**: 80/100
  - 100% of prompts and resources have a non-trivial description (not blank, and not just the item's name).
  - AI-judged instruction clarity (good).
  - Context-footprint check failed: tool/resource definitions use about 1500 tokens (~115/item across 13 items; 10 tools + 3 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 37/100
  - Stability observed for 11 of 30 days with no destabilising changes; credit accrues until the full window elapses.
- **Tool Coverage**: 100/100
  - 100% of tools have a non-trivial description (not blank, and not just the tool's name).
  - 100% of tool parameters carry a description.
- **Tool Safety**: 100/100
  - No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.
  - We read all 10 captured tool definition(s), and no name or description among them implies an irreversible operation.
  - An AI judge read all 11 captured unit(s) of tool text and found none that tries to manipulate the model reading it.
- **Capabilities**: 100/100
  - Implements a supported MCP spec version (2025-11-25); the latest is 2026-07-28.

## Install

### How do I install the Arc MCP server?

Arc runs locally as an npm package, launched with npx -y @hudsonkit/arc-mcp. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.

### Claude

```bash
claude mcp add hudsonkit-arc -- npx -y @hudsonkit/arc-mcp
```

### Cursor

```json
{
  "mcpServers": {
    "hudsonkit-arc": {
      "command": "npx",
      "args": [
        "-y",
        "@hudsonkit/arc-mcp"
      ]
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "hudsonkit-arc": {
      "command": "npx",
      "args": [
        "-y",
        "@hudsonkit/arc-mcp"
      ]
    }
  }
}
```

### Codex

```bash
codex mcp add hudsonkit-arc -- npx -y @hudsonkit/arc-mcp
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "hudsonkit-arc": {
      "type": "local",
      "command": [
        "npx",
        "-y",
        "@hudsonkit/arc-mcp"
      ],
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add hudsonkit-arc --command npx --arg -y --arg @hudsonkit/arc-mcp
```

### Hermes

```yaml
mcp_servers:
  hudsonkit-arc:
    command: "npx"
    args: ["-y", "@hudsonkit/arc-mcp"]
```

### Netclaw

```json
{
  "McpServers": {
    "hudsonkit-arc": {
      "Transport": "stdio",
      "Command": "npx",
      "Arguments": [
        "-y",
        "@hudsonkit/arc-mcp"
      ]
    }
  }
}
```

### Vellum

```bash
assistant mcp add hudsonkit-arc -t stdio -c npx -a -y @hudsonkit/arc-mcp
```

### Other

```json
{
  "mcpServers": {
    "hudsonkit-arc": {
      "command": "npx",
      "args": [
        "-y",
        "@hudsonkit/arc-mcp"
      ]
    }
  }
}
```

## Changelog

Every change recorded for this component, newest first. Days that predate change tracking, or that we cannot explain, say so: "we were watching and nothing happened" and "we were not watching" are different claims.

### 2026-11-05 (score 87, +1)

No change was recorded against any check on this day. Stability & Change Management went from 33 to 37. That category is still filling its 30-day observation window: 10 days of observed history at the previous scan, 11 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-11-02 (score 86, +1)

No change was recorded against any check on this day. Stability & Change Management went from 23 to 27. That category is still filling its 30-day observation window: 7 days of observed history at the previous scan, 8 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-31 (score 85, +1)

No change was recorded against any check on this day. Stability & Change Management went from 17 to 20. That category is still filling its 30-day observation window: 5 days of observed history at the previous scan, 6 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-29 (score 84, +1)

No change was recorded against any check on this day. Stability & Change Management went from 10 to 13. That category is still filling its 30-day observation window: 3 days of observed history at the previous scan, 4 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-27 (score 83, +1)

No change was recorded against any check on this day. Stability & Change Management went from 3 to 7. That category is still filling its 30-day observation window: 1 days of observed history at the previous scan, 2 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-25 (score 82)

First indexed and scored.

## MCP tools (10)

### `validate_diagram` (~81 tokens)

Validate an ArcDiagramData document. Returns coded diagnostics — consume by `code`, apply one `supportedFixes` entry, re-validate. `ok` is false while any error-severity diagnostic remains.

Input parameters:

- `diagram` (object, required): Arc diagram JSON object or JSON string
- `severity` (string): Filter returned diagnostics by severity (default: all)

### `diff_diagram` (~109 tokens)

Structural diff of two Arc diagrams. Returns a DiagramDelta — added/removed/moved/changed nodes, connector adds/removes/changes (keyed by connector id or from→to), connectorStyles and groups deltas, layoutChanged. Feed it to <ArcDiagram data={head} delta={delta} /> for a diff render.

Input parameters:

- `base` (object, required): Base ArcDiagramData JSON object or JSON string
- `head` (object, required): Head ArcDiagramData JSON object or JSON string

### `auto_layout` (~55 tokens)

Run Arc auto-layout on a diagram. Pass a full diagram or minimal input (nodeData + connectors + connectorStyles).

Input parameters:

- `input` (object, required): Full ArcDiagramData or AutoDiagramInput (nodeData, connectors, connectorStyles)

### `render_ascii` (~59 tokens)

Render an Arc diagram as monospace ASCII/Unicode box art.

Input parameters:

- `charset` (string): Character set (default: unicode)
- `diagram` (object, required): Valid ArcDiagramData JSON
- `maxWidth` (integer): Max output width in characters

### `render_svg` (~193 tokens)

Render an Arc diagram as deterministic SVG markup using the package export path.

Input parameters:

- `animateFlows` (boolean): Embed SMIL flow animation in the SVG (default: true; ignored when flowTime is set)
- `backgroundColor` (string): CSS background color (defaults to the theme canvas)
- `diagram` (object, required): Valid ArcDiagramData JSON
- `flowTime` (number): Render flow markers at this route second (disables SMIL animation)
- `includeGrid` (boolean): Render the diagram grid (default: branded themes on, others off)
- `mode` (string): Color mode; defaults to the theme default
- `padding` (number): Padding around the export bounds in px (default: 20)
- `theme` (string): Arc theme id: default, warm, cool, mono, engineering, workbench, tactical, command, spacex, claude, codex, or inherit

### `render_png` (~207 tokens)

Render an Arc diagram as a PNG via an installed Chrome/Chromium binary. Returns MCP image content plus render metadata. Set ARC_CHROME if Chrome is not on PATH.

Input parameters:

- `backgroundColor` (string): CSS background color (defaults to the theme canvas)
- `diagram` (object, required): Valid ArcDiagramData JSON
- `flowTime` (number): Flow route second to freeze into the PNG (default: 0)
- `includeGrid` (boolean): Render the diagram grid (default: branded themes on, others off)
- `mode` (string): Color mode; defaults to the theme default
- `padding` (number): Padding around the export bounds in px (default: 20)
- `scale` (number): Raster scale factor (default: 2, max: 4)
- `theme` (string): Arc theme id: default, warm, cool, mono, engineering, workbench, tactical, command, spacex, claude, codex, or inherit

### `render_animation` (~263 tokens)

Render diagram flows as a GIF or MP4 artifact. Uses deterministic frame captures through Chrome plus ffmpeg; requires an `output` path because video payloads are too large for MCP text.

Input parameters:

- `backgroundColor` (string): CSS background color (defaults to the theme canvas)
- `diagram` (object, required): Valid ArcDiagramData JSON
- `duration` (number): Seconds to render (default: one full flow cycle)
- `format` (string): Output format; inferred from `output` extension when omitted
- `fps` (number): Frames per second (default: 12 for GIF, 30 for MP4)
- `includeGrid` (boolean): Render the diagram grid (default: branded themes on, others off)
- `mode` (string): Color mode; defaults to the theme default
- `output` (string, required): Destination file path for the GIF or MP4
- `padding` (number): Padding around the export bounds in px (default: 20)
- `scale` (number): Raster scale factor (default: 2, max: 4)
- `theme` (string): Arc theme id: default, warm, cool, mono, engineering, workbench, tactical, command, spacex, claude, codex, or inherit

### `render_html` (~331 tokens)

Render an Arc diagram as a React component snippet, iframe embed, or standalone HTML page.

Input parameters:

- `backgroundColor` (string): CSS background color for format=html (defaults to the theme canvas)
- `baseUrl` (string): Studio base URL for format=iframe (default: ARC_EDITOR_URL or http://localhost:5188)
- `componentName` (string): Component function name for format=component (default: ArcDiagramExample)
- `dataName` (string): Diagram const name for format=component (default: diagram)
- `diagram` (object, required): Valid ArcDiagramData JSON
- `format` (string): Output format: component (TSX), iframe (embed tag), or html (standalone SVG page). Default: html
- `height`: Iframe height in px or CSS percentage
- `includeGrid` (boolean): Render the diagram grid for format=html (default: branded themes on, others off)
- `interactive` (boolean): Whether the React component is interactive
- `mode` (string): Color mode; defaults to the theme default
- `padding` (number): Padding around the export bounds in px for format=html (default: 20)
- `sessionId` (string): Session id for format=iframe URLs (generated if omitted)
- `theme` (string): Arc theme id: default, warm, cool, mono, engineering, workbench, tactical, command, spacex, claude, codex, or inherit
- `title` (string): HTML document title or iframe title
- `width`: Iframe width in px or CSS percentage

### `diagram_to_typescript` (~53 tokens)

Convert a valid Arc diagram JSON into a TypeScript module that exports ArcDiagramData.

Input parameters:

- `diagram` (object, required): Valid ArcDiagramData JSON
- `exportName` (string): Const name (default: diagram)

### `editor_handoff` (~105 tokens)

Build URLs to open a diagram in the Arc studio. Returns a hash-based editor URL and showcase link.

Input parameters:

- `baseUrl` (string): Studio base URL (default: ARC_EDITOR_URL or http://localhost:5188)
- `diagram` (object, required): Valid ArcDiagramData JSON
- `sessionId` (string): Session id (generated if omitted)
- `view` (string): Guided view id to start on (data.views[].id) — deep-links the player chapter

## Diagnostics

Captured diagnostic sections: Provenance, Dependencies. The full working is on the page: https://verifymcp.io/servers/hudsonkit-arc/hudsonkit-arc-mcp#diagnostics

## Score history

- 2026-11-05: 87
- 2026-11-04: 86
- 2026-11-03: 86
- 2026-11-02: 86
- 2026-11-01: 85
- 2026-10-31: 85
- 2026-10-30: 84
- 2026-10-29: 84
- 2026-10-28: 83
- 2026-10-27: 83
- 2026-10-26: 82
- 2026-10-25: 82

## Common questions

### What is the Arc MCP server?

Arc is an MCP server listed in the public MCP registry as io.github.hudsonkit/arc. Author, validate, lay out, render, and diff architecture diagrams as code. This page covers its npm package (@hudsonkit/arc-mcp).

### Is the Arc MCP server safe to use?

Arc scores 87 out of 100 on VerifyMCP. We found no known CVEs affecting it as of 5 November 2026. It declares no install or post-install scripts. Its build provenance is signed and verified. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.

### What tools does the Arc MCP server expose?

Arc exposes 10 tools: validate_diagram, diff_diagram, auto_layout, render_ascii, render_svg, and 5 more. Their descriptions and schemas cost roughly 1,456 tokens of context every time the server is loaded.

### Is the Arc MCP server still maintained?

Arc is still listed as active in the MCP registry. We last reached this channel on 5 November 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.

### What licence is the Arc MCP server under?

Arc declares the MIT licence, which is OSI-approved. That covers the source only, and says nothing about the cost of any service it calls.

### What did VerifyMCP test on the Arc MCP server?

VerifyMCP ran 16 checks on Arc, covering Malware scan, Known CVEs, Install scripts, Dependency health and 12 more. Endpoint Security and Transport & Reachability do not apply to an npm package, so they were not tested. The score does not measure everything, and the scoring documentation lists what it leaves out.

## Links

- npm package: https://www.npmjs.com/package/@hudsonkit/arc-mcp
- Socket report: https://socket.dev/npm/package/@hudsonkit/arc-mcp
- Repository: https://github.com/hudsonkit/arc
- Website: https://hudsonkit.com/arc
- Changelog RSS feed: https://verifymcp.io/servers/hudsonkit-arc/hudsonkit-arc-mcp.xml
- Changelog JSON feed: https://verifymcp.io/servers/hudsonkit-arc/hudsonkit-arc-mcp/changelog.json
- Trust report (JSON): https://verifymcp.io/servers/hudsonkit-arc/hudsonkit-arc-mcp.json
- HTML version of this page: https://verifymcp.io/servers/hudsonkit-arc/hudsonkit-arc-mcp