mcp-toolkit

A Model Context Protocol (MCP) server that gives an LLM safe, useful tools: sandboxed file operations, a calculator, and a SQL database interface — plus resources and a prompt template.

Connect it to Claude Desktop, any MCP-compatible client, or talk to it from the included Python client example.

Tools

Related MCP server: lakehouse-mcp

Resources

Prompts

Quickstart

python3 -m venv .venv && source .venv/bin/activate
pip install -r requirements.txt

# Build the sample SQLite database
python3 scripts/build_sample_db.py

# Run the server (stdio transport — what MCP clients expect)
python3 server.py

# Run the tests
pytest -v

Try it with the example client

examples/client_example.py spawns the server over stdio, lists its tools, calls calculate and query_database, and prints the results:

python3 examples/client_example.py

Expected output (abridged):

Tools exposed by the server:
  - list_dir: List files and directories in the sandboxed workspace.
  - read_file: Read a text file from the sandboxed workspace.
  ...
calculate("237 * 41 + 19") -> 9736.0
query_database("SELECT category, COUNT(*) ...") -> [...]

Connect to Claude Desktop

Add this to your Claude Desktop config (~/Library/Application Support/Claude/claude_desktop_config.json on macOS, %APPDATA%\Claude\claude_desktop_config.json on Windows):

{
  "mcpServers": {
    "toolkit": {
      "command": "/absolute/path/to/mcp-toolkit/.venv/bin/python",
      "args": ["/absolute/path/to/mcp-toolkit/server.py"],
      "env": {
        "MCP_WORKSPACE": "/absolute/path/to/mcp-toolkit/workspace"
      }
    }
  }
}

A ready-to-edit template is in examples/claude_desktop_config.json. Restart Claude Desktop and the tools appear in the tool picker.

Safety by design

• Sandboxed filesystem — file tools can only touch MCP_WORKSPACE (defaults to ./workspace); path traversal (..) is rejected.

• Read-only SQL — only SELECT/WITH statements run; anything else is refused before it reaches SQLite.

• Safe calculator — expressions are parsed with ast, not eval; only arithmetic operators, whitelisted math functions, and numbers are allowed.

• No secrets in tools — the server never asks for or handles credentials.

Project structure

mcp-toolkit/
├── server.py                 # MCPServer: tools, resources, prompts
├── tools/
│   ├── filesystem.py         # sandboxed file tools (pure functions)
│   ├── calculator.py         # safe AST-based calculator
│   └── database.py           # read-only SQLite interface
├── scripts/build_sample_db.py# builds data/sample.db (tiny e-commerce data)
├── workspace/                # sandboxed files the tools can touch
├── examples/
│   ├── client_example.py     # stdio client demo
│   └── claude_desktop_config.json
└── tests/test_mcp.py

Why MCP?

MCP is the open standard for connecting LLMs to data and tools — one protocol instead of a bespoke integration per app. This server shows the three MCP primitives: tools (actions the model can call), resources (data the model can read), and prompts (reusable instruction templates).

License

MIT — see LICENSE.