DB MCP Server

DB MCP (HR CSV → SQLite) — Open Source Reference

This folder contains a fully open-source Model Context Protocol (MCP) server implementation that:

• Loads an HR “people” CSV file
• Reads 3 lines of metadata at the top of the CSV (comment lines starting with #)
• Imports the CSV into an in-memory SQLite database
• Exposes read-only MCP tools over stdio (newline-delimited JSON-RPC 2.0)

No Claude Desktop setup is required. A small Python client is included for testing.

Files

• db_mcp_server.py — MCP server (stdio)
• db_mcp_client.py — simple MCP stdio client for testing
• data/hr_people.csv — sample HR CSV with 3-line metadata header

Run the server

python db_mcp_server.py

Optionally pass a custom CSV path:

python db_mcp_server.py /path/to/your/hr_people.csv

Or set an environment variable:

HR_CSV_PATH=/path/to/your/hr_people.csv python db_mcp_server.py

Test with the included client (recommended)

python db_mcp_client.py

You should see:

• initialize handshake
• tools/list
• a sample SQL query result
• an interactive prompt to run more SELECT queries

Tools exposed

• hr_metadata — returns the 3-line metadata header as a JSON object
• hr_schema — returns the SQLite schema for table employees
• hr_query — execute read-only SELECT/WITH SQL queries
• hr_find_people — structured search without writing SQL

CSV metadata format (first 3 lines)

Example:

# dataset: HR People
# description: Synthetic employee roster for MCP demo (no real PII)
# primary_key: employee_id
employee_id,first_name,last_name,...

Metadata lines are parsed as key: value. If a line is not key: value, it is stored as meta_line_1, meta_line_2, etc.

Notes for sharing

• Everything here is standard-library Python (SQLite + CSV).
• The demo data is synthetic (no real PII).
• The server writes only JSON-RPC to stdout. Logs go to stderr (safe for stdio MCP).

Samples

-Terminal 1

C:\Users\davidzhang\Downloads\ml\ml\db_mcp_1>python mcp_server.py data/hr_people.csv
[db_mcp_server] Ready. Loaded data/hr_people.csv. Tools: 4

-Terminal 2
 C:\Users\davidzhang\Downloads\ml\ml\db_mcp_1>python client.py --csv ./data/hr_people.csv
[db_mcp_server] Ready. Loaded ./data/hr_people.csv. Tools: 4
[db_mcp_server] Internal error:
Traceback (most recent call last):
  File "C:\Users\davidzhang\Downloads\ml\ml\db_mcp_1\db_mcp_server.py", line 537, in main
    server.handle(msg)
  File "C:\Users\davidzhang\Downloads\ml\ml\db_mcp_1\db_mcp_server.py", line 493, in handle
    self.handle_initialize(id_value, params)
  File "C:\Users\davidzhang\Downloads\ml\ml\db_mcp_1\db_mcp_server.py", line 438, in handle_initialize
Initialize response:
{
  "jsonrpc": "2.0",
  "error": {
    "code": -32603,
    "message": "Internal error"
  },
  "id": 1
}
    _send(resp)

Tools:
  File "C:\Users\davidzhang\Downloads\ml\ml\db_mcp_1\db_mcp_server.py", line 45, in _send
{
  "jsonrpc": "2.0",
  "id": 2,
  "result": {
    "tools": [
      {
        "name": "hr_metadata",
        "title": "HR dataset metadata",
        "description": "Return the 3-line metadata header read from the HR CSV file.",
        "inputSchema": {
          "type": "object",
          "additionalProperties": false
        },
        "outputSchema": {
          "type": "object"
        }
      },
      {
        "name": "hr_schema",
        "title": "HR table schema",
        "description": "Return SQLite schema information for the employees table.",
        "inputSchema": {
          "type": "object",
          "additionalProperties": false
        },
        "outputSchema": {
          "type": "object"
        }
      },
      {
        "name": "hr_query",
        "title": "Run a read-only SQL query",
        "description": "Execute a read-only SQL query (SELECT/WITH only) against the in-memory SQLite database.
Table name: employees
Example: SELECT department, COUNT(*) AS n FROM employees GROUP BY department",
        "inputSchema": {
          "type": "object",
          "properties": {
            "sql": {
              "type": "string",
              "description": "A SELECT/WITH SQL query to run."
            },
            "limit": {
              "type": "integer",
              "minimum": 1,
              "maximum": 500,
              "description": "Optional row limit (wraps the query)."
            }
          },
          "required": [
            "sql"
          ],
          "additionalProperties": false
        },
        "outputSchema": {
          "type": "object",
          "properties": {
            "rowCount": {
              "type": "integer"
            },
            "rows": {
              "type": "array",
              "items": {
                "type": "object"
              }
            }
          },
          "required": [
            "rowCount",
            "rows"
          ]
        }
      },
      {
        "name": "hr_find