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 skills add shennawardana23/skillme --skill engineering-values-and-tradeoff-principlesgit clone --depth 1 https://github.com/shennawardana23/skillmeWrote 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/shennawardana23/skillme/engineering-values-and-tradeoff-principles)<a href="https://agentmods.dev/skills/shennawardana23/skillme/engineering-values-and-tradeoff-principles"><img src="https://agentmods.dev/badge/skills/shennawardana23/skillme/engineering-values-and-tradeoff-principles/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/shennawardana23/skillme/engineering-values-and-tradeoff-principles"><img src="https://agentmods.dev/badge/skills/shennawardana23/skillme/engineering-values-and-tradeoff-principles.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 | $0.00105 | $0.01386 |
| Opus 5 | $0.00053 | $0.00693 |
| Sonnet 5 | $0.00021 | $0.00277 |
| Haiku 4.5 | $0.00011 | $0.00139 |
Grade A, and why
engineering-values-and-tradeoff-principles 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 11d 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 — 115 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Engineering Values and Tradeoff Principles
Teams that debate "should we prioritize speed or reliability" as an abstract values question tend to relitigate it every release, because nobody wrote down a rule that ends the debate the same way each time. The practical fix demonstrated by Google's Site Reliability Engineering practice: convert the philosophical tradeoff into a measurable, agreed threshold ahead of time, so in the moment it's a lookup, not a debate.
The error budget: reliability vs. velocity as one number
Google SRE's error budget makes this concrete: no service is ever required to be 100% reliable (100% is the wrong target — it eliminates any room to ship changes, since every change carries some risk of an incident, and it costs disproportionately more to chase each additional "nine" of reliability). Instead:
- Set an explicit reliability target below 100% (e.g., 99.9% availability over a rolling window) based on what the product actually needs — a target chosen by asking what unreliability users would actually notice and be harmed by, not by defaulting to the highest number that sounds impressive.
- The gap between the target and 100% is the error budget — the amount of unreliability "spent" on this service is allowed within the window before it's considered a problem.
- Spend the budget on deliberate risk: shipping features, running experiments, doing risky migrations — anything that might cause an incident is implicitly "spending" budget.
- When the budget is exhausted, the pre-agreed policy activates automatically — commonly a freeze on further risky releases until reliability recovers back within budget. This is what makes it operational rather than aspirational: the rule was agreed before the pressure of "we really need to ship this" existed, so it isn't renegotiated under that pressure.
The key move, generalizable beyond SRE: pick the tradeoff's threshold while calm, write it down, and let the written threshold — not a fresh argument each time — decide in the moment the tradeoff actually arises.
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 11d ago First seen · 115 lines · 105 tokens per session scan A b35193396561
engineering-values-and-tradeoff-principles is a skill published in the GitHub repository shennawardana23/skillme (2 stars, last pushed 14d ago), licensed Apache-2.0. It adds 105 tokens to every session and 1,386 once invoked, about $0.0005 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 2026-08-31.
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