github/copilot-plugins is GitHub's collection of extensions for GitHub Copilot, including reusable skills, hooks, MCP servers, and other tools that add capabilities to the coding assistant. It provides workflows and building blocks for using or creating Copilot plugins.
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 github/copilot-plugins --skill build-performance-analysisgit clone --depth 1 https://github.com/github/copilot-pluginsWrote 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/github/copilot-plugins/build-performance-analysis)<a href="https://agentmods.dev/skills/github/copilot-plugins/build-performance-analysis"><img src="https://agentmods.dev/badge/skills/github/copilot-plugins/build-performance-analysis/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/github/copilot-plugins/build-performance-analysis"><img src="https://agentmods.dev/badge/skills/github/copilot-plugins/build-performance-analysis.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 2 findings, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high System Prompt Leakage · line 93 Skill contains instructions that could directly expose system prompts, internal rules, or hidden instructions to users or external parties.Fix: Remove any instructions that reveal, print, or output system prompts or internal rules. System instructions should never be exposed to end users.
- medium Excessive Agency · line 60 Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.Fix: Add human-in-the-loop confirmation for destructive, irreversible, or high-impact operations. Never auto-execute commands that modify files, send data, or alter system state.
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 | $0.00079 | $0.07931 |
| Opus 5.5 | $0.00032 | $0.03172 |
| Sonnet 5.5 | $0.00016 | $0.01586 |
| Haiku 4.5 | $0.00008 | $0.00793 |
Grade B, and why
build-performance-analysis scanned grade B with 1 finding 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 1mo 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.
Asks the agent to reveal its instructionsmediumSystem prompt leakage
Directions to print, repeat or translate the system prompt extract configuration the operator did not intend to expose.
If neither check is true, you MUST get explicit consent before launching an elevated process. **Use the `ask_user` tool — never just print prompt text in chat.** How it starts
The opening of the file, as written. The whole thing — 602 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Build Performance Analysis with vcperf.exe
Execution order
A single workflow, always run in order.
Workflow — always run, in order
Treat each session as independent. Re-capture traces, JSON analysis, and baseline measurements fresh each session instead of reusing data from a previous session — the one-time trace-permission grant persists.
- Prerequisites: Trace Permission — grant ETW rights. Run before any workspace exploration (project enumeration, file listing, code search).
- Core Workflow + The /jsonAnalysis Flag
- Baseline Measurement — 5 uninstrumented clean rebuilds of the pre-change state; average for a stable baseline. Make no code or project edits during this step.
- Remediation Strategies — the first step where you edit anything; apply changes informed by Steps 2–3.
- Measuring Final Performance Improvement — 5 uninstrumented clean rebuilds of the post-change state; compare against the baseline. If a PCH or template change shows a neutral or regressed delta, also run Iterative Build Measurement.
Which vcperf.exe executable should I use?
The sessionStart hook installs vcperf.exe under %LOCALAPPDATA%\vcperf\build-perf-cpp (multiple versions may coexist). Resolve the newest version once and reuse it:
$vcperfPkg = Get-ChildItem "$env:LOCALAPPDATA\vcperf\build-perf-cpp" -Directory -Filter 'Microsoft.Cpp.vcperf.*' -ErrorAction SilentlyContinue | Sort-Object { ($_.Name -replace '^Microsoft\.Cpp\.vcperf\.', '' -split '\.' | ForEach-Object { ([long]$_).ToString().PadLeft(20, '0') }) -join '.' } -Descending | Select-Object -First 1
$vcperf = if ($vcperfPkg) { (Get-ChildItem $vcperfPkg.FullName -Recurse -Filter vcperf.exe | Where-Object DirectoryName -like '*\x64' | Select-Object -First 1).FullName }
What ships with it
2 files 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.
- 1mo ago First seen · 602 lines · 79 tokens per session scan B b6fd0b2f4a21
build-performance-analysis is a skill published in the GitHub repository github/copilot-plugins (377 stars, last pushed 14d ago), licensed MIT. It adds 79 tokens to every session and 7,931 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it B with 1 finding (asks the agent to reveal its instructions). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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