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 skills/attemainio/dotnet-toolkit/dotnet-performancenpx skills add Attemainio/dotnet-toolkit --skill dotnet-performancegit clone --depth 1 https://github.com/Attemainio/dotnet-toolkitWhat 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 | $0.00376 | $0.10861 |
| Opus 5 | $0.00188 | $0.05431 |
| Sonnet 5 | $0.00075 | $0.02172 |
| Haiku 4.5 | $0.00038 | $0.01086 |
Grade A, and why
dotnet-performance 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 2d 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 — 590 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Measuring what this plugin costs against not having it
dotnet-selfeval asks whether the tools are efficient against each other — which route inside the
plugin is cheapest. This skill asks the prior question: is the plugin cheaper than not using it, in
this repo, on this kind of task — and does a real, unrestricted session actually behave the way an
idealized best-case or worst-case comparison assumes? Those are three different questions, and they
can disagree. A tool can be the best route inside the plugin and still lose to grep on a repo of forty
files; a guard that only advises can still go unheeded even when it is right.
The claim under test is the one in the always-loaded rule: that text search gives wrong answers on C#, not merely slower ones, and that the MCP tools cost fewer tokens than the file reads they replace. The first half is a correctness claim and the second is a cost claim. Measure them separately — a route that is cheaper and wrong is not a win, and reporting a single blended number hides exactly that case. A third claim, added when this skill grew a third probe, is a practice claim: does a real session, free to use either tool family and free to ignore an advisory nudge, actually land closer to the ceiling or closer to the floor? A benchmark that only ever plays the two extremes cannot answer that on its own.
Why three subagents, not the orchestrator playing all the routes
A single Claude instance that designs the outcomes, answers them through the MCP tools, and then plays another route is contaminated by construction: by the time the second route runs, the answer is already sitting in context, whether or not it's used deliberately. A route played by an agent who just saw the answer is not what a session without that head start actually produces, and no amount of self-instruction to "not look at the answer" closes that gap reliably.
The fix is three independently-spawned agents, none with any memory of this conversation or of the others' runs:
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.
- 2d ago First seen · 590 lines · 376 tokens per session scan A 1fe7bdb3da20
dotnet-performance is a skill published in the GitHub repository Attemainio/dotnet-toolkit (2 stars, last pushed 6d ago), licensed MIT. It adds 376 tokens to every session and 10,861 once invoked, about $0.0019 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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