Database Scout Skill for Claude

database-scout

Read-only exploration tool for SQLite / PostgreSQL databases — inspect table schemas, preview data, generate ER diagrams, and run safe queries.

Feature Overview

| Feature | Description |

|---------|-------------|

| List all tables | Show tables and views in the database, with row counts |

| Inspect table schema | Column names, types, constraints (PK/FK/NOT NULL), indexes, defaults |

| Data preview | View the first N rows of a table |

| ER diagram generation | Output Mermaid erDiagram syntax, ready to render |

| Safe read-only queries | Only SELECT/WITH/EXPLAIN allowed; write operations are blocked |

Security Mechanisms

• Connection-level read-only: SQLite opens with ?mode=ro URI; PostgreSQL uses SET SESSION READ ONLY
• SQL whitelist: Only statements starting with SELECT / WITH / EXPLAIN / PRAGMA / SHOW are allowed
• Dangerous keyword blocking: INSERT, UPDATE, DELETE, DROP, ALTER, CREATE, and 30+ other keywords are blocked
• Multi-statement blocking: Semicolon-separated multiple SQL statements are rejected (prevents injection)
• Identifier escaping: Table names are double-quote escaped to prevent SQL injection

Quick Start

# List all tables in a SQLite database
python3 scripts/db_explorer.py --db-path data.db list-tables

# Inspect table schema
python3 scripts/db_explorer.py --db-path data.db describe users

# Preview data (default 20 rows)
python3 scripts/db_explorer.py --db-path data.db preview orders --limit 10

# Generate Mermaid ER diagram
python3 scripts/db_explorer.py --db-path data.db er-diagram

# Run a read-only query
python3 scripts/db_explorer.py --db-path data.db query "SELECT name, age FROM users WHERE age > 18 LIMIT 10"

PostgreSQL

# Connect to PostgreSQL
python3 scripts/db_explorer.py --db-type postgres --dsn "host=localhost dbname=mydb user=reader" list-tables

# Inspect table schema
python3 scripts/db_explorer.py --db-type postgres --dsn "host=localhost dbname=mydb user=reader" describe orders

Detailed Usage

Parameters

| Parameter | Required | Default | Description |

|-----------|----------|---------|-------------|

| --db-type | No | sqlite | Database type: sqlite or postgres |

| --db-path | Yes (for SQLite) | — | Path to the SQLite database file |

| --dsn | Yes (for PostgreSQL) | — | PostgreSQL connection string |

Subcommands

| Command | Description | Example |

|---------|-------------|---------|

| list-tables | List all tables/views | list-tables |

| describe <table> | Show detailed table schema | describe users |

| preview <table> [--limit N / -n N] | Preview the first N rows | preview orders --limit 5 |

| er-diagram | Generate Mermaid ER diagram | er-diagram |

| query "<sql>" | Run a read-only SQL query | query "SELECT count(*) FROM users" |

Output Examples

list-tables

[
  {"name": "users", "type": "table", "row_count": 1500},
  {"name": "orders", "type": "table", "row_count": 8200},
  {"name": "user_stats", "type": "view", "row_count": 1500}
]

describe

{
  "table": "orders",
  "row_count": 8200,
  "columns": [
    {"cid": 0, "name": "id", "type": "INTEGER", "notnull": true, "default": null, "primary_key": true},
    {"cid": 1, "name": "user_id", "type": "INTEGER", "notnull": true, "default": null, "primary_key": false},
    {"cid": 2, "name": "amount", "type": "REAL", "notnull": false, "default": "0.0", "primary_key": false}
  ],
  "foreign_keys": [
    {"from": "user_id", "to_table": "users", "to_column": "id"}
  ],
  "indexes": [
    {"name": "idx_orders_user_id", "unique": false, "columns": ["user_id"]}
  ]
}

er-diagram (Mermaid)

erDiagram
    users {
        INTEGER id PK
        TEXT name
        TEXT email
        INTEGER age
    }
    orders {
        INTEGER id PK
        INTEGER user_id FK
        REAL amount
        TEXT created_at
    }
    users ||--o{ orders : "user_id"

Dependencies

• Python 3.8+ (sqlite3 is a built-in module)
• PostgreSQL support requires: pip install psycopg2-binary