mcp-datalink

@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