pilat/mcp-datalink

MCP server for PostgreSQL, MySQL, and SQLite. Gives AI assistants secure database access via Model Context Protocol.

npx @pilat/mcp-datalink

Works with Claude Desktop, Claude Code, Cursor, Cline, and any MCP-compatible client.

Installation

Add to your MCP client config file (see config locations below):

{
  "mcpServers": {
    "datalink": {
      "command": "npx",
      "args": ["-y", "@pilat/mcp-datalink"],
      "env": {
        "DATALINK_ANALYTICS_URL": "postgresql://user:password@localhost:5432/analytics",
        "DATALINK_ANALYTICS_READONLY": "true",

        "DATALINK_INVENTORY_URL": "mysql://user:password@localhost:3306/inventory",

        "DATALINK_CACHE_URL": "sqlite:///path/to/cache.db"
      }
    }
  }
}

This creates three database connections: analytics (read-only), inventory, and cache.

Variable	Description
DATALINK_{NAME}_URL	Connection URL (creates database named {name})
DATALINK_{NAME}_READONLY	Set to true to block writes
DATALINK_{NAME}_MAX_TIMEOUT	Max query timeout in ms (caps model requests)

Connection URL formats:

# PostgreSQL
postgresql://user:password@localhost:5432/dbname
postgresql://user:password@localhost:5432/dbname?sslmode=require

# MySQL
mysql://user:password@localhost:3306/dbname
mysql://user:password@localhost:3306/dbname?ssl=true

# SQLite
sqlite:///path/to/database.db
sqlite:///Users/me/data/app.sqlite
sqlite://../relative/path/data.db

Environment Variable Substitution

URLs support ${VAR} syntax to reference other environment variables:

{
  "mcpServers": {
    "datalink": {
      "command": "npx",
      "args": ["-y", "@pilat/mcp-datalink"],
      "env": {
        "DATALINK_MAIN_URL": "${DATABASE_URL}"
      }
    }
  }
}

This allows reusing existing environment variables (like DATABASE_URL from your shell or .env file).

Supported syntax:

Syntax	Description
${VAR}	Expands to value of VAR, or keeps ${VAR} if unset
${VAR:-default}	Expands to value of VAR, or default if unset

Examples:

# Reference existing DATABASE_URL
DATALINK_MAIN_URL="${DATABASE_URL}"

# Build URL from parts
DATALINK_MAIN_URL="postgresql://${DB_USER}:${DB_PASS}@${DB_HOST}:5432/mydb"

# With default values
DATALINK_MAIN_URL="postgresql://localhost:${DB_PORT:-5432}/mydb"

Config File Locations

Client	Config file
Claude Code	~/.claude.json (global) or .mcp.json (project)
Claude Desktop (macOS)	~/Library/Application Support/Claude/claude_desktop_config.json
Claude Desktop (Windows)	%APPDATA%\Claude\claude_desktop_config.json
Cursor	~/.cursor/mcp.json or Settings → Features → MCP Servers
Cline	cline_mcp_settings.json or VS Code settings cline.mcpServers

Tools

Tool	Description
list_databases	List configured database connections
list_tables	List tables with row counts
describe_table	Get schema, indexes, foreign keys
query	Run SELECT queries
execute	Run INSERT/UPDATE/DELETE
explain	Show query execution plans

Security

• Prepared statements only (no SQL injection)
• Single statement per query (no chaining)
• DDL blocked (no DROP, ALTER, TRUNCATE)
• Readonly mode per connection
• Response size limit (100 rows, 64KB default, configurable via DATALINK_MAX_TOTAL_SIZE)
• Query timeout: 30s default, model can request up to 10min, MAX_TIMEOUT caps it

License

MIT