eric861129/mssql

MSSQL Read-Only Query Skill

Execute safe, read-only queries against configured Microsoft SQL Server databases.

Requirements

• Python 3.8+
• pymssql: pip install -r requirements.txt

Setup

Create connections.json in the skill directory or ~/.config/claude/mssql-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": 1433,
      "database": "app_prod",
      "user": "readonly_user",
      "password": "your-password",
      "encrypt": true,
      "tds_version": "7.3"
    }
  ]
}

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: 1433) | | database | Yes | Database name | | user | Yes | Username | | password | Yes | Password | | encrypt | No | Enable TLS encryption (default: false) | | tds_version | No | TDS protocol version: 7.0, 7.1, 7.2, 7.3, 7.4 (default: auto) |

Usage

List configured databases

python3 scripts/query.py --list

Query a database

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

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

Note: MSSQL uses TOP N instead of LIMIT. The --limit flag automatically inserts TOP N after SELECT.

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 enforcement: Query validation blocks write operations (use a db_datareader role user for server-side protection)
• Query validation: Only SELECT, SHOW, EXPLAIN, WITH, SP_HELP queries allowed
• Single statement: Multiple statements per query rejected
• TLS support: Configurable encryption for secure connections
• Query timeout: 30-second timeout enforced via pymssql
• Connection timeout: 10-second login timeout
• 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 | | TDS version error | Try "tds_version": "7.3" or "7.4" | | Encryption error | Set "encrypt": true for Azure SQL | | Permission warning | Run chmod 600 connections.json |

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 (auto-converts to TOP N)