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

Field	Required	Description
name	Yes	Identifier for the database (case-insensitive)
description	Yes	What data this database contains (used for auto-selection)
host	Yes	Database hostname
port	No	Port number (default: 3306)
database	Yes	Database name
user	Yes	Username
password	Yes	Password
ssl_disabled	No	Set to `true` to disable SSL (default: false)
ssl_ca	No	Path to CA certificate file
ssl_cert	No	Path to client certificate file
ssl_key	No	Path to client private key file

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:

User asks about	Look for description containing
users, accounts	users, accounts, customers
orders, sales	orders, transactions, sales
analytics, metrics	analytics, metrics, reports
logs, events	logs, events, audit

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

Error	Solution
Config not found	Create `connections.json` in skill directory
Authentication failed	Check username/password in config
Connection timeout	Verify host/port, check firewall/VPN
SSL error	Try `"ssl_disabled": true` for local databases
Permission warning	Run `chmod 600 connections.json`
max_execution_time not supported	Upgrade to MySQL 5.7.8+ or MariaDB 10.1.1+

Exit Codes

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

Workflow

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