How to Write a Claude Code Skill: Templates and Best Practices

# Skill: Write Database Migration

## Description
Use this skill when asked to add, rename, or modify database tables or columns.
Applies to: Prisma migrations, schema changes, data migrations.

## Context
- ORM: Prisma 5.x
- Database: PostgreSQL 16
- Migration files: `prisma/migrations/`
- Naming: `[timestamp]_[description]` (auto-generated by Prisma)
- Schema file: `prisma/schema.prisma`

@prisma/schema.prisma

## Instructions
1. Read the current schema in `prisma/schema.prisma` to understand existing models
2. Make the minimal schema change needed — do not refactor unrelated models
3. For new columns on existing tables with data, always provide a default value
4. Run: `pnpm prisma migrate dev --name [descriptive-name]` to generate the migration
5. Review the generated SQL in `prisma/migrations/[timestamp]_[name]/migration.sql`
6. If the migration changes enum values, write a separate data migration script
7. Run `pnpm prisma generate` to update the client types

## Rules
- NEVER change a column's type directly — add a new column, migrate data, then drop the old one
- NEVER write raw SQL migration files by hand — always use `prisma migrate dev`
- ALWAYS check that the generated migration is reversible

## Example
Request: "Add a `bio` column to the User model"

Schema change:
```prisma
model User {
  id    String @id @default(cuid())
  email String @unique
  name  String
  bio   String? @db.Text  // Added
}
```

Command to run:
```bash
pnpm prisma migrate dev --name add_user_bio
```

# Skill: Write PR Description

## Description
Use this skill when asked to write a GitHub pull request description.
Invoke when: creating a PR, updating PR description, summarizing changes.

## Instructions
1. Run `git log origin/main...HEAD --oneline` to list commits
2. Run `git diff origin/main...HEAD --stat` to see changed files
3. Read the 3-5 most important changed files to understand the change
4. Write the PR description following the template below

## Template
```markdown
## Summary
<!-- 2-3 sentences: what changed and why -->

## Changes
- <!-- bullet list of specific changes -->

## Testing
- [ ] Unit tests pass (`pnpm test`)
- [ ] Manual testing done (describe what you tested)
- [ ] No regressions in related features

## Screenshots
<!-- If UI changes, add before/after screenshots -->
```

## Rules
- Keep Summary to 2-3 sentences — no more
- List changes as specific bullets, not vague phrases like 'improved performance'
- Always include the testing checklist
- Never use jargon that a non-author reviewer wouldn't understand