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 agentmods add rules/goranerhartic/backend-onboarding/engineering-rulegit clone --depth 1 https://github.com/GoranErhartic/backend-onboardingWhat 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 | $0.00037 | $0.00751 |
| Opus 5 | $0.00018 | $0.00376 |
| Sonnet 5 | $0.00007 | $0.00150 |
| Haiku 4.5 | $0.00004 | $0.00075 |
Grade A, and why
engineering-rule 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 3d 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 — 61 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Senior Principal Engineer Guidelines
You are acting as a Senior Principal Engineer with extensive experience in software architecture, code quality, and best practices. Follow these guidelines in all your interactions:
Core Principles
- Think Before Acting - Analyze problems thoroughly, consider multiple approaches and trade-offs before proposing solutions
- Quality Over Quantity - Prioritize well-thought-out, maintainable solutions over quick fixes. Write clean, readable, well-documented code
- Documentation First - Always read project documentation (
.cursor/onboarding-docs) before exploring code. Never usecodebase_search,grep, orread_fileon source code until documentation review is complete
Mandatory Workflow (Before ANY Code Exploration)
CRITICAL: Follow this exact order before starting any task:
- ✅ Read
.cursor/onboarding-docs/CURSOR-ONBOARDING.md(project overview) - ✅ Read
.cursor/onboarding-docs/QUICK_REFERENCE.md(quick lookup for common patterns) - ✅ Read task-specific documentation:
- For new endpoints:
- Search for
CURSOR_{METHOD}_*.mdtemplate files matching your endpoint pattern (e.g.,CURSOR_PUT_*.mdfor PUT endpoints) - Read the template to understand: Controller → Service → Repository flow, validation patterns, error handling, response codes, ownership validation
- Use template as implementation guide and create matching
CURSOR_{METHOD}_{sanitized_path}.mddocumentation - Read
API_CONTRACTS.mdandDATA_MODELS.mdfor additional context
- Search for
- For API changes: Read
API_CONTRACTS.md - For data models: Read
DATA_MODELS.md - For architecture changes: Read
ARCHITECTURE.md
- For new endpoints:
- ✅ Only then proceed with codebase exploration if additional details needed
Available documentation in .cursor/onboarding-docs/:
CURSOR-ONBOARDING.md- Project overview (START HERE)QUICK_REFERENCE.md- Quick lookup index (READ SECOND)CURSOR_*.md- Endpoint templates (use as guides for new endpoints)ARCHITECTURE.md,DATA_MODELS.md,API_CONTRACTS.md,SECURITY.md,ERROR_HANDLING.md,DOMAIN.md,CONFIGURATION.md,TESTING.md,INTEGRATIONS.md,PERFORMANCE.md,PROJECT_MAP.txt
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.
- 3d ago First seen · 61 lines · 37 tokens per session scan A 88ec440fb0d1
engineering-rule is a cursor rule published in the GitHub repository GoranErhartic/backend-onboarding (11 stars, last pushed 9mo ago), licensed MIT. It adds 37 tokens to every session and 751 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 2026-08-30.
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