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/thesethrose/devrules/02-common-errorsgit clone --depth 1 https://github.com/TheSethRose/DevRulesWhat 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 | $0.00273 | $0.00273 |
| Opus 5 | $0.00137 | $0.00137 |
| Sonnet 5 | $0.00055 | $0.00055 |
| Haiku 4.5 | $0.00027 | $0.00027 |
Grade A, and why
02-common-errors 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.
What it actually says
Common Mistakes & Anti-Patterns for This Project
This file lists patterns the AI should actively avoid when working on this specific codebase.
Format Guide:
Use the following structure for each entry:
### MISTAKE: [Short Description of the Mistake]
- [PATTERN]: Describe when or how the mistake typically occurs.
- [BAD_EXAMPLE]: (Optional) Show a concise code snippet of the incorrect way.
- [GOOD_EXAMPLE]: Show a concise code snippet of the correct way.
- [SOLUTION/RULE]: Clearly state the rule or the correct approach to follow.
- [CONTEXT/REASON]: (Optional) Explain why the correct way is preferred (e.g., performance, maintainability, project standard).
- [REFERENCE]: (Optional) Link to relevant documentation, style guide section, or issue tracker.
Project-Specific Mistakes (User: Add your entries below)
MISTAKE:
- [PATTERN]:
- [BAD_EXAMPLE]:
- [GOOD_EXAMPLE]:
- [SOLUTION/RULE]:
- [CONTEXT/REASON]:
- [REFERENCE]:
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 · 32 lines · 273 tokens per session scan A 01c960134a95
02-common-errors is a cursor rule published in the GitHub repository TheSethRose/DevRules (25 stars, last pushed 1y ago), licensed MIT. It adds 273 tokens to every session, about $0.0014 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.
Other cursor rules, from other repositories
creating-cursor-rules
Meta-rule for creating effective Cursor IDE rules with best practices, patterns, and examples.
prpm-json-best-practices
Best practices for structuring prpm.json package manifests with required fields, tags, organization, and multi-package management.
creating-skills
Meta-guide for creating effective Claude Code skills with proper structure, CSO optimization, and real examples.
beanstalk-deploy
Robust deployment patterns for Elastic Beanstalk with GitHub Actions, Pulumi, and edge case handling.
core-principles
Core development principles for building PRPM (Prompt Package Manager).
creating-kiro-agents
Kiro agent configuration patterns, JSON structure, tool permissions, and security best practices for creating specialized AI development assistants.