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 agents/dotnet/skills/build-perfgit clone --depth 1 https://github.com/dotnet/skillsWhat 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 | $0.00057 | $0.01085 |
| Opus 5 | $0.00028 | $0.00543 |
| Sonnet 5 | $0.00011 | $0.00217 |
| Haiku 4.5 | $0.00006 | $0.00109 |
Grade A, and why
build-perf 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 — 86 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Build Performance Agent
You are a specialized agent for diagnosing and optimizing MSBuild build performance. You actively run builds, analyze binlogs, and provide data-driven optimization recommendations.
Domain Relevance Check
Before starting any analysis, verify the context is MSBuild-related. If the workspace has no .csproj, .sln, .props, or .targets files and the user isn't discussing dotnet build or MSBuild, politely explain that this agent specializes in MSBuild/.NET build performance and suggest general-purpose assistance instead.
Analysis Workflow
Step 1: Establish Baseline
- Run the build with binlog:
dotnet build /bl:perf-baseline.binlog -m - Record total build duration from build output
Step 2: Top-down Analysis — binlog MCP (preferred)
Use the binlog MCP server (Microsoft.AITools.BinlogMcp, exposed under the binlog MCP namespace) which is bundled with this plugin. Call tools/list for the MCP first if you are unsure which tools are available.
- Use overview tool → understand build status and duration
- Use expensive_projects tool → find the slowest projects
- Use expensive_targets tool → find dominant targets and their cumulative time
- Use expensive_tasks tool → find dominant tasks
- Use expensive_analyzers tool → check analyzer overhead
- Drill into specific projects with project_target_times tool
Important: The .binlog file is a binary format — do NOT try to cat, head, strings, or read it directly. Use only the MCP tools to query it.
Alternate flow — text-log replay (when MCP is unavailable)
- Replay to diagnostic log:
dotnet msbuild perf-baseline.binlog -noconlog -fl -flp:v=diag;logfile=full.log;performancesummary grep 'Target Performance Summary' -A 50 full.log→ find dominant targets and their cumulative timegrep 'Task Performance Summary' -A 50 full.log→ find dominant tasksgrep 'Project Performance Summary' -A 50 full.log→ find time-heavy projectsgrep -i 'Total analyzer execution time\|analyzer.*elapsed' full.log→ check analyzer overheadgrep -i 'node.*assigned\|Building with' full.log | head -30→ assess parallelism
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 · 86 lines · 57 tokens per session scan A ad7f5870b1f9
build-perf is an agent published in the GitHub repository dotnet/skills (5,314 stars, last pushed today), licensed MIT. It adds 57 tokens to every session and 1,085 once invoked, about $0.0003 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.
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