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
1---2name: mysql-23description: Execute read-only SQL queries against multiple MySQL databases. Use when: (1) querying MySQL databases, (2) exploring database schemas/tables, (3) running SELECT queries for data analysis, (4) checking database contents. Supports multiple database connections with descriptions for intelligent auto-selection. Blocks all write operations (INSERT, UPDATE, DELETE, DROP, etc.) for safety.4license: Apache-2.05---6
7# MySQL Read-Only Query Skill
8
9Execute safe, read-only queries against configured MySQL databases.
10
11## Requirements
12
13- Python 3.8+
14- mysql-connector-python: `pip install -r requirements.txt`
15
16## Setup
17
18Create `connections.json` in the skill directory or `~/.config/claude/mysql-connections.json`.
19
20**Security**: Set file permissions to `600` since it contains credentials:
21```bash
22chmod 600 connections.json
23```
24
25```json
26{
27 "databases": [
28 {
29 "name": "production",
30 "description": "Main app database - users, orders, transactions",
31 "host": "db.example.com",
32 "port": 3306,
33 "database": "app_prod",
34 "user": "readonly_user",
35 "password": "your-password",
36 "ssl_disabled": false
37 }
38 ]
39}
40```
41
42### Config Fields
43
44| Field | Required | Description |
45|-------|----------|-------------|
46| name | Yes | Identifier for the database (case-insensitive) |
47| description | Yes | What data this database contains (used for auto-selection) |
48| host | Yes | Database hostname |
49| port | No | Port number (default: 3306) |
50| database | Yes | Database name |
51| user | Yes | Username |
52| password | Yes | Password |
53| ssl_disabled | No | Set to `true` to disable SSL (default: false) |
54| ssl_ca | No | Path to CA certificate file |
55| ssl_cert | No | Path to client certificate file |
56| ssl_key | No | Path to client private key file |
57
58## Usage
59
60### List configured databases
61```bash
62python3 scripts/query.py --list
63```
64
65### Query a database
66```bash
67python3 scripts/query.py --db production --query "SELECT * FROM users LIMIT 10"
68```
69
70### List tables
71```bash
72python3 scripts/query.py --db production --tables
73```
74
75### Show schema
76```bash
77python3 scripts/query.py --db production --schema
78```
79
80### Limit results
81```bash
82python3 scripts/query.py --db production --query "SELECT * FROM orders" --limit 100
83```
84
85## Database Selection
86
87Match user intent to database `description`:
88
89| User asks about | Look for description containing |
90|-----------------|--------------------------------|
91| users, accounts | users, accounts, customers |
92| orders, sales | orders, transactions, sales |
93| analytics, metrics | analytics, metrics, reports |
94| logs, events | logs, events, audit |
95
96If unclear, run `--list` and ask user which database.
97
98## Safety Features
99
100- **Read-only session**: Connection uses MySQL `SET SESSION TRANSACTION READ ONLY` (primary protection)
101- **Query validation**: Only SELECT, SHOW, DESCRIBE, EXPLAIN, WITH queries allowed
102- **Single statement**: Multiple statements per query rejected
103- **SSL support**: Configurable SSL with CA, client cert, and key support
104- **Query timeout**: 30-second max_execution_time enforced (MySQL 5.7.8+)
105- **Memory protection**: Max 10,000 rows per query to prevent OOM
106- **Column width cap**: 100 char max per column for readable output
107- **Credential sanitization**: Error messages don't leak passwords
108
109## Troubleshooting
110
111| Error | Solution |
112|-------|----------|
113| Config not found | Create `connections.json` in skill directory |
114| Authentication failed | Check username/password in config |
115| Connection timeout | Verify host/port, check firewall/VPN |
116| SSL error | Try `"ssl_disabled": true` for local databases |
117| Permission warning | Run `chmod 600 connections.json` |
118| max_execution_time not supported | Upgrade to MySQL 5.7.8+ or MariaDB 10.1.1+ |
119
120## Exit Codes
121
122- **0**: Success
123- **1**: Error (config missing, auth failed, invalid query, database error)
124
125## Workflow
126
1271. Run `--list` to show available databases
1282. Match user intent to database description
1293. Run `--tables` or `--schema` to explore structure
1304. Execute query with appropriate LIMIT
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