Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add kumaran-is/claude-code-onboarding --skill database-schema-designergit clone --depth 1 https://github.com/kumaran-is/claude-code-onboardingWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/kumaran-is/claude-code-onboarding/database-schema-designer)<a href="https://agentmods.dev/skills/kumaran-is/claude-code-onboarding/database-schema-designer"><img src="https://agentmods.dev/badge/skills/kumaran-is/claude-code-onboarding/database-schema-designer/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/kumaran-is/claude-code-onboarding/database-schema-designer"><img src="https://agentmods.dev/badge/skills/kumaran-is/claude-code-onboarding/database-schema-designer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00036 | $0.01616 |
| Opus 5 | $0.00018 | $0.00808 |
| Sonnet 5 | $0.00007 | $0.00323 |
| Haiku 4.5 | $0.00004 | $0.00162 |
Grade A, and why
database-schema-designer scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 6d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 165 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Iron Law
NO SCHEMA MIGRATION WITHOUT A DOWN (ROLLBACK) SCRIPT AND AN INDEX ON EVERY FOREIGN KEY — unindexed FKs cause full table scans; irreversible migrations cause production incidents
Database Schema Designer
Design production-ready database schemas with best practices built-in.
Triggers
| Trigger | Example |
|---|---|
design schema |
"design a schema for user authentication" |
database design |
"database design for multi-tenant SaaS" |
create tables |
"create tables for a blog system" |
schema for |
"schema for inventory management" |
model data |
"model data for real-time analytics" |
I need a database |
"I need a database for tracking orders" |
design NoSQL |
"design NoSQL schema for product catalog" |
Quick Reference
| Task | Approach | Key Consideration |
|---|---|---|
| New schema | Normalize to 3NF first | Domain modeling over UI |
| SQL vs NoSQL | Access patterns decide | Read/write ratio matters |
| Primary keys | INT or UUID | UUID for distributed systems |
| Foreign keys | Always constrain | ON DELETE strategy critical |
| Indexes | FKs + WHERE columns | Column order matters |
| Migrations | Always reversible | Backward compatible first |
Process
Phase 1: Analyze
- Identify entities and relationships
- Determine access patterns (read-heavy vs write-heavy)
- Choose SQL or NoSQL based on requirements
Phase 2: Design
- Normalize to 3NF (SQL) or determine embed/reference strategy (NoSQL)
- Define primary keys and foreign keys
- Choose appropriate data types -- read
reference/data-types-reference.mdfor type guides - Add constraints -- read
reference/constraints-and-relationships.mdfor patterns
Read reference/normalization-guide.md for 1NF/2NF/3NF rules and examples.
Phase 3: Optimize
- Plan indexing strategy -- read
reference/indexing-strategy.mdfor when to index and composite index rules - Consider denormalization for read-heavy queries
- Add timestamps (created_at, updated_at)
What ships with it
12 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
- assets/templates/migration-template.sql 1.9 KB
- reference/backup-restoration-drill.md 4.2 KB
- reference/constraints-and-relationships.md 5.2 KB
- reference/data-types-reference.md 4.0 KB
- reference/expand-contract-migrations.md 4.4 KB
- reference/firestore-storage-security.md 6.3 KB
- reference/indexing-strategy.md 5.0 KB
- reference/migration-patterns.md 5.1 KB
- reference/normalization-guide.md 3.7 KB
- reference/nosql-design-patterns.md 4.6 KB
- reference/postgresql-review-checklist.md 3.1 KB
- reference/schema-design-checklist.md 3.3 KB
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 6d ago First seen · 165 lines · 36 tokens per session scan A 3817cd8debb8
database-schema-designer is a skill published in the GitHub repository kumaran-is/claude-code-onboarding (35 stars, last pushed 2mo ago), licensed MIT. It adds 36 tokens to every session and 1,616 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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