SQL Data MCP Server

A custom Model Context Protocol (MCP) server that gives Claude Desktop direct access to a SQLite database — enabling natural language questions to be answered through real, live SQL execution.

What This Does

Instead of copy-pasting data into a chat, this server exposes a local SQLite database as a set of tools Claude can call directly. Ask a question in plain English, and Claude decides which tool to use, writes the SQL, executes it against the real database, and returns the results.

Tools Exposed

list_tables() — Lists all tables in the database
describe_table(table_name) — Shows column names and types for a given table
run_query(sql) — Executes a read-only SELECT query and returns the results

Tech Stack

Python with the official mcp SDK (FastMCP)
SQLite for the local database
Claude Desktop as the MCP Host

How It Works

Claude Desktop is configured (via claude_desktop_config.json) to launch this server as a subprocess. Each Python function decorated with @mcp.tool() is automatically exposed to Claude — the decorator reads the function's name, type hints, and docstring to build the tool schema, so no manual JSON schema writing is required.

When a user asks a question, Claude reasons about which tool to call, requests permission to run it, executes it, and uses the real result to answer — genuine tool use, not a simulated response.

Setup

Clone this repo
Install dependencies: pip install -r requirements.txt
Build the database: python create_db.py
Add this server to your claude_desktop_config.json:

{
  "mcpServers": {
    "sql-data-server": {
      "command": "/path/to/python.exe",
      "args": ["/path/to/server.py"]
    }
  }
}

Fully restart Claude Desktop
Ask Claude a question about your data — e.g. "What tables are available, and what's the average purchase amount by customer segment?"

Note on Paths

server.py computes the database path relative to its own file location (os.path.dirname(os.path.abspath(__file__))) rather than assuming a working directory — this ensures it works correctly regardless of what directory the MCP Host launches the process from.