Kastell vs Captcha MCP

In-depth architectural comparison of the Kastell and Captcha MCP 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.

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).
• Primary tools included: Server security audits with remediation, SSH hardening and fail2ban setup, UFW firewall management.

Explore Kastell Details

Choose Captcha MCP 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: CAPTCHA_URL, HTTP_MODE, PORT.
• Primary tools included: Challenge, verify, and status MCP tools, SHA-256 proof-of-work free tier, L402 Lightning payment support.

Feature & Specification Comparison

Specification	Kastell kastelldev Security	Captcha MCP zekebuilds-lab 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.	L402 Lightning paywall + Hashcash proof-of-work gate for MCP tool calls. Free tier solves a PoW challenge; paid tier pays a Lightning invoice via self-hosted LNBits. No accounts, no API keys, no third-party SaaS. Drop-in middleware for any MCP server. npx @powforge/captcha-mcp.
Category & Scope

Tools & Capabilities Breakdown

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).

{
  "mcpServers": {
    "kastelldev-kastell": {
      "command": "npx",
      "args": [
        "-y",
        "kastell"
      ]
    }
  }
}

{
  "mcpServers": {
    "zekebuilds-lab-captcha-mcp": {
      "command": "npx",
      "args": [
        "-y",
        "@powforge/captcha-mcp"
      ],
      "env": {
        "CAPTCHA_URL": "YOUR_CAPTCHA_URL_HERE",
        "HTTP_MODE": "YOUR_HTTP_MODE_HERE",
        "PORT": "YOUR_PORT_HERE"
      }
    }
  }
}

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