Schema designer

Skill batterfried-philosophy172/Agent-Startup-Skills/skills/schema-designer

Build SaaS products using an 8-phase AI agent pipeline with mandatory approval gates for Antigravity, Claude Code, and Codex.

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npx -y skills add batterfried-philosophy172/Agent-Startup-Skills --skill schema-designer

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Database schema design agent that creates complete data models with tables, relationships, indexes, and seed data. Triggers on: database design, schema, data model, tables, ERD, entity relationship, database schema.

SKILL.md

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Schema Designer — Data Modeling Agent

Purpose

Design a complete, normalized database schema before coding begins. Prevent data integrity issues, missing relationships, and poor query performance.

When to Use

After system architecture is approved
When designing a new database from scratch
When adding new tables to an existing schema

Process

Step 1: Entity Identification

From the MVP feature list, identify every "thing" the system stores:

Users, Products, Orders, Subscriptions, etc.

Step 2: Table Definitions

For each entity, define the complete table:

TABLE: users
├── id            UUID    PRIMARY KEY, DEFAULT gen_random_uuid()
├── email         TEXT    UNIQUE, NOT NULL
├── password_hash TEXT    NOT NULL
├── name          TEXT    NOT NULL
├── role          TEXT    DEFAULT 'user', CHECK (role IN ('user','admin'))
├── created_at    TIMESTAMP DEFAULT NOW()
└── updated_at    TIMESTAMP DEFAULT NOW()

Step 3: Relationships

Define all foreign keys and relationships:

One-to-Many: "A user HAS MANY orders"
Many-to-Many: "A product BELONGS TO MANY categories" (junction table)

Step 4: Indexes

Add indexes for:

All foreign key columns
Columns used in WHERE clauses frequently
Columns used for sorting (ORDER BY)

Step 5: Seed Data

Provide 2-3 sample rows per table for testing.

Rules

Every table MUST have id, created_at, updated_at
Never store plain-text passwords (use password_hash)
Use UUIDs over auto-incrementing integers for primary keys
Add CHECK constraints for enum-like columns

Output

Produce a schema.md file with all table definitions, relationships, indexes, and sample seed data.

Exit Criteria

Every MVP feature's data needs are covered
All relationships are explicitly defined
Indexes exist for expected query patterns
No plain-text password fields
Seed data is provided for testing