What is the key difference between Kastell and Arai?

Kastell belongs to the Security category with local stdio execution, while Arai belongs to the Security category with local stdio execution.

How do I install Kastell or Arai in Claude Desktop or Cursor?

Copy the mcpServers JSON configuration snippet provided on this page into your claude_desktop_config.json or ~/.cursor/mcp.json file and restart your AI client.

Are Kastell and Arai free or paid?

Kastell operates under a Free / Open Source model (No auth required). Arai operates under a Free / Open Source model (No auth required).

Which MCP server has more tools and community activity?

Kastell lists 6 tools with 2 views and 56 GitHub stars. Arai lists 6 tools with 1 views and 7 GitHub stars.

Can I use both Kastell and Arai together in the same MCP host?

Yes! MCP hosts like Claude Desktop, Cursor, Windsurf, Cline, and VS Code support configuring multiple servers under the mcpServers object simultaneously.

How do I install Kastell or Arai in Claude Desktop, Cursor, or Windsurf?

Both servers follow the standard Model Context Protocol configuration format. Simply copy the JSON block from the configuration section above and paste it into your AI client's mcpServers configuration object (for instance in claude_desktop_config.json or ~/.cursor/mcp.json ), then completely restart or refresh the application.

Are Kastell and Arai free to use, or do they require API keys?

Kastell is listed under a Free / Open Source model with No auth required . Arai operates under a Free / Open Source model with No auth required . If environment variables are required (such as API keys), be sure to define them under the env key in your MCP client's configuration file.

Can I run both Kastell and Arai at the same time in my AI client?

Yes! MCP clients support multi-server orchestration. You can include both kastelldev-kastell and taniwhaai-arai as distinct keys inside the single mcpServers object in your configuration file. Your AI assistant will automatically select and call the appropriate tool from either server during chat sessions.

Which MCP server has higher directory engagement and quality ratings?

On AllMCPs, Kastell has a Quality Score of 52 /100 ( Good ) with 2 views, 0 installs, and 56 GitHub stars. Arai holds a Quality Score of 49 /100 ( Fair ) with 1 views, 0 installs, and 7 GitHub stars.

Side-by-Side Model Context Protocol Comparison

Kastell vs Arai

In-depth architectural comparison of the Kastell and Arai MCP servers. Compare execution transports, security boundaries, tool capabilities, quality scores, and ready-to-paste client installation snippets for Claude, Cursor, Windsurf, and VS Code.

At a Glance & Executive Verdict

Kastell

Security · Local stdio

Quality: 52/100 (Good) | Auth: No auth required

Arai

Security · Local stdio

Quality: 49/100 (Fair) | Auth: No auth required

Verdict Summary: Choose Kastell if you need specialized Security tools running via a local process. Choose Arai if your workspace requires Security integration with local subprocess execution. Both servers can be configured concurrently in your client's mcpServers manifest.

Which MCP Server Should You Choose?

Choose Kastell when:

You need dedicated capabilities in the Security domain.
You prefer local stdio subprocess transport architecture.
Your security boundary fits: No auth required (Free / Open Source).
You have access to required keys: KASTELL_API_KEY, KASTELL_PROVIDER_TOKEN, KASTELL_SSH_KEY_PATH, KASTELL_CONFIG_PATH.
Primary tools included: 413 security checks in 29 categories, Automated safe fixes and 19-step production hardening, Compliance mapping to CIS, PCI-DSS, HIPAA.

Explore Kastell Details

Choose Arai when:

You need dedicated capabilities in the Security domain.
You prefer local stdio subprocess transport architecture.
Your security boundary fits: No auth required (Free / Open Source).
You have access to required keys: ARAI_TELEMETRY_OPTOUT.
Primary tools included: .

Feature & Specification Comparison

Specification	Kastell kastelldev Security	Arai taniwhaai Security
Summary	Server security auditing and hardening toolkit. 413 security checks across 29 categories (SSH, Firewall, Docker, TLS, HTTP Headers), CIS/PCI-DSS/HIPAA compliance mapping, 19-step production hardening, fleet management, and forensic evidence collection. Supports Hetzner, DigitalOcean, Vultr, and Linode. 13 MCP tools.	Policy enforcement for AI coding agents derived from existing instruction files (CLAUDE.md, .cursorrules, .windsurfrules, .github/copilot-instructions.md) — no separate YAML to maintain. Rules with prohibitive predicates (never, forbids, mustnot) emit permissionDecision: deny to block tool calls in Claude Code; advisory rules inject context. PostToolUse is correlated with PreToolUse to produce per-rule obeyed/ignored compliance verdicts in a local JSONL audit log. MCP tools — araiaddguard (register rules mid-session), arailistguards, arairecentdecisions — work in any MCP client (Claude Desktop, Cursor, Windsurf, Cline). No network on the hook hot path; opt-out anonymous telemetry.

Tools & Capabilities Breakdown

Kastell Tools (6)

413 security checks in 29 categories

Automated safe fixes and 19-step production hardening

Compliance mapping to CIS, PCI-DSS, HIPAA

Fleet management with multi-server support

Built-in MCP server with 17 AI tools

Support for Hetzner, DigitalOcean, Vultr, Linode

Arai Tools (6)

Ready-to-Paste Client Configurations

Paste either (or both) of these JSON server blocks into your client config file (e.g. claude_desktop_config.json or ~/.cursor/mcp.json).

Kastell Configuration

mcpServers (Claude Desktop / Cursor)

{
  "mcpServers": {
    "kastelldev-kastell": {
      "command": "npx",
      "args": [
        "-y",
        "kastelldev-kastell"
      ],
      "env": {
        "KASTELL_API_KEY": "YOUR_KASTELL_API_KEY_HERE",
        "KASTELL_PROVIDER_TOKEN": "YOUR_KASTELL_PROVIDER_TOKEN_HERE",
        "KASTELL_SSH_KEY_PATH": "YOUR_KASTELL_SSH_KEY_PATH_HERE",
        "KASTELL_CONFIG_PATH": "YOUR_KASTELL_CONFIG_PATH_HERE"
      }
    }
  }
}

Arai Configuration

mcpServers (Claude Desktop / Cursor)

{
  "mcpServers": {
    "taniwhaai-arai": {
      "command": "npx",
      "args": [
        "-y",
        "taniwhaai-arai"
      ],
      "env": {
        "ARAI_TELEMETRY_OPTOUT": "YOUR_ARAI_TELEMETRY_OPTOUT_HERE"
      }
    }
  }
}

Frequently Asked Questions

Kastell is categorized under Security and uses a local stdio subprocess. In contrast, Arai belongs to Security using local stdio subprocess. Select Kastell when you need capabilities focused on security and Arai when you require tools for security.

More alternatives to Kastell More alternatives to Arai Security category hub