GeraTools MCP Server

An MCP server that gives AI agents — Claude Desktop, Claude Code, ChatGPT with tools, Cursor, Windsurf, or any MCP client — a set of everyday developer utilities from GeraTools: Base64, cryptographic hashing, regex testing, word count, JWT decoding and CSS unit conversion.

Every tool is a pure, deterministic function ported straight from the published GeraTools browser tools (or Node's crypto). No backend, no network, no auth — everything runs locally, so an agent can compute these without leaving the machine.

Tools

| Tool | What it does | |------|--------------| | base64 | Encode text/hex to Base64, or decode Base64 / Base64url to text. UTF-8 safe (emoji round-trip), standard + URL-safe variants, hex fallback for non-text bytes. | | hash | Cryptographic digest: md5, sha1, sha256, sha384, sha512. Input as utf8/hex/base64; output as hex/base64. | | regex_test | Run a JS regex against a string — returns every match with index, capture groups, named groups, count, and a plain-English explanation of the pattern. | | word_count | Words, characters (with/without spaces), sentences, paragraphs, lines, and 200-wpm reading time. | | jwt_decode | Base64url-decode a JWT into header + payload, list iat/nbf/exp as ISO timestamps, and report expiry. (Does not verify the signature.) | | css_unit_convert | Convert a CSS length between px, rem, em, pt, pc, in, cm, mm, Q (1in = 96px; rem/em respect configurable font sizes). |

Install & run

# Run directly (no global install) once published to npm:
npx -y @gera-services/mcp-geratools

# Or from this repo:
cd packages/mcp-geratools
npm run build      # tsc --noCheck  -> dist/
node bin/cli.js    # starts on stdio

Client configuration

Claude Desktop / Claude Code (claude_desktop_config.json)

{
  "mcpServers": {
    "geratools": {
      "command": "npx",
      "args": ["-y", "@gera-services/mcp-geratools"]
    }
  }
}

Local (unpublished) variant — point at the built CLI:

{
  "mcpServers": {
    "geratools": {
      "command": "node",
      "args": ["/Users/armen/Gera/packages/mcp-geratools/bin/cli.js"]
    }
  }
}

Cursor / Windsurf (.cursor/mcp.json etc.)

{
  "mcpServers": {
    "geratools": {
      "command": "npx",
      "args": ["-y", "@gera-services/mcp-geratools"]
    }
  }
}

Verify it works

npm run build
node scripts/smoke.mjs

The smoke test speaks raw MCP JSON-RPC over stdio (initialize → tools/list → a real tools/call for every tool) and asserts the results — including a Base64 emoji round-trip, the known SHA-256 of "abc", and 16px == 1rem. Expected output ends with ALL SMOKE CHECKS PASSED.

Examples

Ask your agent:

• "Base64-encode this string for me" → base64 (mode encode)
• "What's the SHA-256 of this file's contents?" → hash (sha256)
• "Does \b\w+@\w+\.\w+\b match these two emails, and what does it mean?" → regex_test
• "Decode this JWT and tell me when it expires" → jwt_decode
• "How many rem is 24px at a 18px root?" → css_unit_convert

License

MIT © Gera Systems Ltd