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.
git clone --depth 1 https://github.com/levifig/rails-instructionsWrote 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/rules/levifig/rails-instructions/models)<a href="https://agentmods.dev/rules/levifig/rails-instructions/models"><img src="https://agentmods.dev/badge/rules/levifig/rails-instructions/models/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/rules/levifig/rails-instructions/models"><img src="https://agentmods.dev/badge/rules/levifig/rails-instructions/models.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 | $0.00000 | $0.00940 |
| Opus 5.5 | $0.00000 | $0.00376 |
| Sonnet 5.5 | $0.00000 | $0.00188 |
| Haiku 4.5 | $0.00000 | $0.00094 |
Grade A, and why
models 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.
How it starts
The opening of the file, as written. The whole thing — 157 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Rails Models and Active Record Guide
Core Philosophy
- Models are the heart of your Rails application
- Keep business logic and data integrity in models
- Use database constraints to enforce rules
- Design for clarity and maintainability
- Trust Active Record's conventions
Model Design Principles
- Focus models on their core domain responsibility
- Keep models cohesive and loosely coupled
- Use descriptive names that reflect business concepts
- Avoid God objects - split large models when needed
- Document complex business rules clearly
Schema Management
- Always use the annotate gem for schema documentation
- Keep schema annotations at the top of model files
- Run annotate after every migration
- Review schema changes carefully before committing
- Document non-obvious column purposes
Model Organization
- Order model contents consistently for readability
- Place constants at the top
- Group related elements together
- Keep public interface minimal
- Document complex logic thoroughly
Associations Best Practices
- Define all relationships explicitly
- Use appropriate dependent options
- Consider bi-directional associations carefully
- Avoid circular dependencies
- Document association purposes when not obvious
Validation Strategy
- Validate at the model level always
- Use database constraints to match validations
- Keep validation messages user-friendly
- Group related validations together
- Test all validation scenarios
Database Constraints
- Add NOT NULL constraints for required fields
- Use unique indexes for uniqueness validations
- Implement foreign key constraints
- Add check constraints for complex rules
- Document constraint purposes in migrations
Scopes and Queries
- Create scopes for commonly used queries
- Keep scope names descriptive and intention-revealing
- Chain scopes for complex queries
- Avoid scopes with side effects
- Use class methods for scopes with parameters
Callbacks Guidelines
- Use callbacks sparingly and purposefully
- Keep callback methods private
- Avoid callbacks that touch other models
- Document callback purposes clearly
- Consider service objects for complex workflows
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 · 157 lines · 0 tokens per session scan A 3601bf241d62
models is a cursor rule published in the GitHub repository levifig/rails-instructions (56 stars, last pushed 1y ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 940 tokens. 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 2026-08-30.
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