PostgreSQL

A CLI tool for exploring and debugging PostgreSQL databases with JSON-first output designed for AI agents.

CLI Discovery

The CLI is located at ./scripts/pgtool-cli/ relative to this SKILL.md file.

Platform	Script
Unix/Linux/macOS	pgtool
Windows	pgtool.ps1

Claude Code: Use ${CLAUDE_PLUGIN_ROOT}/skills/pgtool/scripts/pgtool-cli/pgtool (or pgtool.ps1 on Windows).

For setup instructions, see SETUP.md in this directory.

Important

• Always use pgtool-cli for all database operations. Do NOT use psql directly.
• If pgtool-cli encounters an error or limitation, report the issue to the user and stop. Do not fall back to psql or other tools.
• Always add LIMIT to SELECT queries to avoid fetching excessive data.

Commands

List Schemas

pgtool schemas

Output: {"ok":true,"schemas":[{"name":"public","owner":"postgres"}]}

List Tables

# Tables in default schema
pgtool tables

# Tables in a specific schema
pgtool tables auth

Output: {"ok":true,"schema":"public","tables":[{"name":"users","type":"table","rowEstimate":1000,"sizeHuman":"256 KB"}]}

Describe Table

Get column details with primary key and foreign key information.

# Table in default schema
pgtool describe users

# Table in specific schema
pgtool describe auth.users

Output includes column types, nullability, defaults, PK/FK info, and foreign key references.

List Indexes

pgtool indexes users

Output: {"ok":true,"indexes":[{"name":"users_pkey","unique":true,"primary":true,"columns":["id"],"type":"btree"}]}

List Constraints

pgtool constraints users

Output includes PRIMARY KEY, FOREIGN KEY, UNIQUE, CHECK, and EXCLUDE constraints.

List Relationships

Get all foreign key relationships in a schema.

pgtool relationships
pgtool relationships auth

Output: {"ok":true,"relationships":[{"fromTable":"orders","fromColumns":["user_id"],"toTable":"users","toColumns":["id"]}]}

Execute Query

pgtool query "SELECT * FROM users WHERE active = true LIMIT 100"

Output: {"ok":true,"rows":[...],"rowCount":5,"fields":["id","name","email"]}

Best Practices:

• Always add LIMIT to SELECT queries to avoid fetching excessive data
• DML statements (INSERT, UPDATE, DELETE) with RETURNING are fully supported
• Use parameterized values in WHERE clauses to avoid SQL injection

Sample Table Rows

Get sample data from a table quickly.

# Default: 5 rows
pgtool sample users

# Custom limit
pgtool sample users --limit 10

# Specific schema
pgtool sample auth.users

Output: {"ok":true,"schema":"public","table":"users","rows":[...],"rowCount":5,"columns":["id","name","email"]}

Count Table Rows

Get exact row count (not estimate).

pgtool count users
pgtool count auth.sessions

Output: {"ok":true,"schema":"public","table":"users","count":12345}

Plain: public.users: 12,345 rows

Search Tables and Columns

Find tables and columns matching a pattern.

pgtool search email
pgtool search user

Output:

{
  "ok": true,
  "pattern": "email",
  "matches": {
    "tables": [{ "schema": "public", "name": "emails" }],
    "columns": [
      {
        "schema": "public",
        "table": "users",
        "column": "email",
        "type": "varchar(255)"
      },
      {
        "schema": "public",
        "table": "contacts",
        "column": "email_address",
        "type": "text"
      }
    ]
  }
}

Schema Overview

Compact ERD-like view showing tables, primary keys, and relationships.

pgtool overview
pgtool overview auth

Output (plain):

Schema: public (3 tables)

users (1.2k rows)
  PK: id
  → orders.user_id, profiles.user_id

orders (45k rows)
  PK: id
  FK: user_id → users.id
  → order_items.order_id

products (500 rows)
  PK: id

Explain Query Plan

Analyze query execution plan.

# With ANALYZE (executes query)
pgtool explain "SELECT * FROM users WHERE email = 'x'"

# Without ANALYZE (plan only)
pgtool explain "SELECT * FROM users WHERE id = 1" --no-analyze

Output: {"ok":true,"query":"SELECT...","plan":["Seq Scan on users...","..."]}

Error Responses

All errors follow a consistent JSON format with ok: false, an error code, and a helpful hint:

Configuration not found:

{
  "ok": false,
  "error": "Configuration file not found",
  "code": "CONFIG_NOT_FOUND",
  "hint": "Create a .pgtool.json file in your project root with database connection details."
}

Connection failed:

{
  "ok": false,
  "error": "Could not connect to database server: connect ECONNREFUSED 127.0.0.1:5432",
  "code": "CONNECTION_FAILED",
  "hint": "Verify host and port in .pgtool.json and ensure PostgreSQL is running"
}

Authentication failed:

{
  "ok": false,
  "error": "Authentication failed",
  "code": "PERMISSION_DENIED",
  "hint": "Check your username and password in .pgtool.json"
}

Table not found:

{
  "ok": false,
  "error": "relation \"nonexistent_table\" does not exist",
  "code": "TABLE_NOT_FOUND",
  "hint": "Check that the table exists and you have permission to access it"
}

Error codes: CONFIG_NOT_FOUND, CONFIG_INVALID, CONNECTION_FAILED, QUERY_FAILED, TABLE_NOT_FOUND, SCHEMA_NOT_FOUND, PERMISSION_DENIED, TIMEOUT

Common Usage Patterns

Exploring a new database:

1. pgtool schemas - See available schemas
2. pgtool overview - Quick view of tables and relationships
3. pgtool tables <schema> - List tables with sizes
4. pgtool describe <table> - Understand table structures
5. pgtool sample <table> - See example data

Finding data:

1. pgtool search <pattern> - Find tables/columns by name
2. pgtool sample <table> - Quick data preview
3. pgtool count <table> - Get exact row count
4. pgtool query "SELECT..." - Custom queries

Debugging data issues:

1. pgtool describe <table> - Verify column types
2. pgtool sample <table> - Check actual data
3. pgtool explain "SELECT..." - Analyze query performance
4. pgtool indexes <table> - Check index coverage

Understanding relationships:

1. pgtool overview - Visual relationship map
2. pgtool relationships - Get all FK relationships
3. pgtool constraints <table> - See specific table constraints