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 joao-aires/agent-skills-public --skill database-designgit clone --depth 1 https://github.com/joao-aires/agent-skills-publicWrote 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/joao-aires/agent-skills-public/database-design)<a href="https://agentmods.dev/skills/joao-aires/agent-skills-public/database-design"><img src="https://agentmods.dev/badge/skills/joao-aires/agent-skills-public/database-design/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/joao-aires/agent-skills-public/database-design"><img src="https://agentmods.dev/badge/skills/joao-aires/agent-skills-public/database-design.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 | $0.00755 |
| Opus 5.5 | $0.00014 | $0.00302 |
| Sonnet 5.5 | $0.00007 | $0.00151 |
| Haiku 4.5 | $0.00004 | $0.00076 |
Grade A, and why
database-design 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 yesterday.
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 — 61 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Design data around invariants and use
Start with the accepted domain, workloads and data lifecycle. Identify authoritative records, derived representations, ownership, access paths and the consequences of stale, missing or conflicting data. Preserve the selected storage model unless evidence and scope justify changing it. A small schema change need not reopen the entire architecture.
Choose representations and consistency boundaries
Invariants
Describe the facts that must still be true after any accepted operation, including concurrent operations. Identify how records are recognized, which values must be unique, which relationships are valid, and who owns the data. Distinguish an application convenience from a rule whose violation would make stored state invalid.
Put enforceable invariants in the durable store when it can express them. Keep application coordination for rules that span operations or external systems, and explain how a partial failure is detected and recovered. This makes the schema and transaction decisions follow from the domain rather than from a list of preferred data types.
- Determine which guarantees belong in durable constraints and which need coordinated application behavior.
- Consider deletion, history and correction semantics before choosing keys and references.
- Document units, precision, null/absent meanings and time semantics where ambiguity changes behavior.
Storage and derived representations
Use expected reads, writes, distribution, growth and failure tolerance to compare relational, document, key/value, object, search or analytical storage.
- Extra representations carry synchronization and recovery costs.
- Treat replicas, caches and indexes as derived until their authority and consistency contract are explicit.
- Workload or availability requirements must justify denormalization, partitioning or a new engine.
Atomic operations
Identify which changes must become visible together for the business result to be valid. Follow two operations that can overlap and ask what happens when each reads the old state before either writes. Choose constraints, conditional writes, locks or transaction isolation that preserve the actual rule, and define whether a conflict is rejected, retried or merged.
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.
- yesterday First seen · 61 lines · 36 tokens per session scan A bc3f3fcad0c0
database-design is a skill published in the GitHub repository joao-aires/agent-skills-public (2 stars, last pushed yesterday), licensed MIT. It adds 36 tokens to every session and 755 once invoked, about $0.0001 per session on Opus 5.5. 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 2026-10-21.
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A tool for operating PostgreSQL databases hosted by Volcano Engine's managed database service. PostgreSQL is a relational database used to store structured application data.