@pilat/mcp-datalink

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

Terminal

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):

config.json

{
  "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:

bash

# 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:

config.json

{
  "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:

bash

# 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