Borrowing it
Nothing to install: this file belongs to Sma1lboy/rove. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/Sma1lboy/rove/main/.agents/skills/pstack/skills/principle-subtract-before-you-add/SKILL.mdgit clone --depth 1 https://github.com/Sma1lboy/roveWrote 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/sma1lboy/rove/principle-subtract-before-you-add)<a href="https://agentmods.dev/skills/sma1lboy/rove/principle-subtract-before-you-add"><img src="https://agentmods.dev/badge/skills/sma1lboy/rove/principle-subtract-before-you-add/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/sma1lboy/rove/principle-subtract-before-you-add"><img src="https://agentmods.dev/badge/skills/sma1lboy/rove/principle-subtract-before-you-add.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 | $0.00039 | $0.00266 |
| Opus 5 | $0.00019 | $0.00133 |
| Sonnet 5 | $0.00008 | $0.00053 |
| Haiku 4.5 | $0.00004 | $0.00027 |
Grade A, and why
principle-subtract-before-you-add 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 12d 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
97% identical to principle-subtract-before-you-add — 4 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.
What it actually says
Subtract Before You Add
When evolving a system, remove complexity first, then build. Deletion gives you a simpler base, which makes the next addition smaller and less brittle.
Why: Adding to a complex system compounds complexity. Removing first cuts the surface area, reveals the essential structure, and usually makes the next design obvious. Default to subtraction.
Make simplification a continual investment. Leave the design slightly simpler and more capable behind the same or smaller surface than you found it.
The pattern:
- Sequence removal before construction
- Cut before you polish (get to the minimum before investing in quality)
- Design for observed usage, not speculative edge cases
- No speculative validators, parsers, or guards beyond what the spec demands
- Out-of-spec features drag validators behind them. Persistence, retry-on-startup, and schema migration each need guards to defend their inputs.
- Simplify prompts (remove redundant instructions, excessive templates)
- When a reference has no novel content, delete it rather than leaving a stub
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.
- 12d ago First seen · 25 lines · 39 tokens per session scan A f4a10763f1cd
principle-subtract-before-you-add is a skill published in the GitHub repository Sma1lboy/rove (127 stars, last pushed today), licensed MIT. It adds 39 tokens to every session and 266 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 97% identical to principle-subtract-before-you-add, differing in 4 lines, and is treated as a copy.
Other skills, from other repositories
fable-recover
Diagnose repeated command failures, stale build caches, branch drift, or contradictory evidence before attempting further code edits. Use when commands fail repeatedly, tests stay red after attempted fixes, build output contradicts source code, or the execution path is confused — even if the user does not explicitly…
debug
Use when diagnosing software errors, test failures, or unexpected runtime behavior.
learner
Post-debugging knowledge extraction — captures non-obvious, codebase-specific learnings that pass quality gates. Invoke after resolving tricky bugs or discovering surprising behavior.
error-tracing
Read stack traces, follow error chains, and trace errors to their root cause. Use when the user encounters an error message, stack trace, exception, or crash. Apply when debugging async errors, React error boundaries, source map issues, or when an error message is unclear.
log-analysis
Implement structured logging and analyze logs to diagnose issues. Use when the user sets up logging, asks about log levels, needs to trace requests through distributed systems, or is analyzing log output to debug a problem. Apply when adding logging to any application.
systematic-debugging
Apply structured debugging techniques to find and fix bugs efficiently. Use when the user reports a bug, encounters unexpected behavior, says something is "not working", or asks for help debugging. Apply hypothesis-driven debugging instead of random changes.