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 wewpellex21/code-sensei --skill databasesgit clone --depth 1 https://github.com/wewpellex21/code-senseiWrote 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/wewpellex21/code-sensei/databases)<a href="https://agentmods.dev/skills/wewpellex21/code-sensei/databases"><img src="https://agentmods.dev/badge/skills/wewpellex21/code-sensei/databases/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/wewpellex21/code-sensei/databases"><img src="https://agentmods.dev/badge/skills/wewpellex21/code-sensei/databases.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 | $0.00035 | $0.00703 |
| Opus 5.5 | $0.00014 | $0.00281 |
| Sonnet 5.5 | $0.00007 | $0.00141 |
| Haiku 4.5 | $0.00003 | $0.00070 |
Grade A, and why
databases 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 1mo 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.
This is a copy
100% identical to databases — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 45 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Databases — CodeSensei Teaching Module
What is a Database?
- Analogy: A super-powered spreadsheet that your app can read and write to automatically. Each "table" is like a sheet, each "row" is an entry, each "column" is a field.
- Key insight: Without a database, your app forgets everything when it restarts. Databases make data PERMANENT.
SQL (Structured Query Language)
- Analogy: SQL is the language you use to talk to the database. Like asking a librarian: "Find me all books by this author, sorted by year."
- Essential operations:
SELECT— "Show me data" →SELECT * FROM users(show all users)INSERT— "Add new data" →INSERT INTO users (name, email) VALUES ('Juan', '[email protected]')UPDATE— "Change existing data" →UPDATE users SET name = 'Juan C' WHERE id = 1DELETE— "Remove data" →DELETE FROM users WHERE id = 1WHERE— "But only the ones that match this condition"
- Quiz: "Which SQL word would you use to find all users who signed up today?"
Types of Databases
- PostgreSQL — the reliable all-rounder. Most vibecoded apps use this. Think of it as Excel but 1000x more powerful.
- SQLite — a lightweight database stored in a single file. Good for small projects. Like a notepad vs a full filing system.
- MongoDB — stores data as flexible documents (JSON-like) instead of rigid tables. Like storing folders of papers vs a spreadsheet.
ORMs (Object-Relational Mappers)
- Analogy: An ORM is a translator between your code and the database. Instead of writing SQL directly, you write code in your programming language and the ORM converts it to SQL.
- Prisma (most common in vibecoded projects):
prisma.user.findMany()→ becomesSELECT * FROM usersprisma.user.create({ data: { name: "Juan" } })→ becomesINSERT INTO users...
- Key insight: ORMs make databases easier to work with, but the SQL is still happening underneath.
Schemas & Migrations
- Schema — the blueprint of your database. Defines what tables exist and what columns each has.
- Migration — a change to the blueprint. Like remodeling a room — you write instructions for the change, then apply them.
- Analogy: The schema is your building's floor plan. A migration is the renovation permit that says "add a new room here."
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.
- 1mo ago First seen · 45 lines · 35 tokens per session scan A 39fa5dbec91f
databases is a skill published in the GitHub repository wewpellex21/code-sensei (3 stars, last pushed 12d ago), licensed MIT. It adds 35 tokens to every session and 703 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 100% identical to databases, differing in 0 lines, and is treated as a copy.
Other skills, from other repositories
java-jpa
Reviews Spring Data JPA for N+1 queries, fetch strategies, projections, and Specifications. Use when user asks to "review JPA", "check for N+1", "JPA performance", "review my entities", "check fetch strategy", or "review my repositories".
java-cache
Use when the user asks to add caching, configure Redis or Caffeine cache, use @Cacheable/@CacheEvict/@CachePut, optimize repeated database or API calls, or review existing Spring Boot cache configuration.
cloudflare-d1
Cloudflare D1 serverless SQLite on edge. Use for databases, migrations, bindings, or encountering D1ERROR, statement too long, too many requests queued errors.
bun-sqlite
Use for bun:sqlite, SQLite operations, prepared statements, transactions, and queries.
bun-redis
Use when working with Redis in Bun (ioredis, Upstash), caching, pub/sub, session storage, or key-value operations.
cloudflare-hyperdrive
Cloudflare Hyperdrive for Workers-to-database connections with pooling and caching. Use for PostgreSQL/MySQL, Drizzle/Prisma, or encountering pool errors, TLS issues, connection refused.