MySQL Read-Only Query Skill

Execute safe, read-only queries against configured MySQL databases.

Requirements

• Python 3.8+
• mysql-connector-python: pip install -r requirements.txt

Setup

Create connections.json in the skill directory or ~/.config/claude/mysql-connections.json.

Security: Set file permissions to 600 since it contains credentials:

chmod 600 connections.json

{
  "databases": [
    {
      "name": "production",
      "description": "Main app database - users, orders, transactions",
      "host": "db.example.com",
      "port": 3306,
      "database": "app_prod",
      "user": "readonly_user",
      "password": "your-password",
      "ssl_disabled": false
    }
  ]
}

Config Fields

Usage

List configured databases

python3 scripts/query.py --list

Query a database

python3 scripts/query.py --db production --query "SELECT * FROM users LIMIT 10"

List tables

python3 scripts/query.py --db production --tables

Show schema

python3 scripts/query.py --db production --schema

Limit results

python3 scripts/query.py --db production --query "SELECT * FROM orders" --limit 100

Database Selection

Match user intent to database description:

If unclear, run --list and ask user which database.

Safety Features

• Read-only session: Connection uses MySQL SET SESSION TRANSACTION READ ONLY (primary protection)
• Query validation: Only SELECT, SHOW, DESCRIBE, EXPLAIN, WITH queries allowed
• Single statement: Multiple statements per query rejected
• SSL support: Configurable SSL with CA, client cert, and key support
• Query timeout: 30-second max_execution_time enforced (MySQL 5.7.8+)
• Memory protection: Max 10,000 rows per query to prevent OOM
• Column width cap: 100 char max per column for readable output
• Credential sanitization: Error messages don't leak passwords

Troubleshooting

Exit Codes

• 0: Success
• 1: Error (config missing, auth failed, invalid query, database error)

Workflow

1. Run --list to show available databases
2. Match user intent to database description
3. Run --tables or --schema to explore structure
4. Execute query with appropriate LIMIT