.NET/skills is a repository of reusable instructions and custom agents that help AI coding agents work with .NET and C#. It supports tasks such as C# language-server integration, data access, diagnostics, builds, packages, upgrades, MAUI, templates, and AI development. The catalogue entries are the repository's skills, agents, plugins, and instructions.
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.
git clone --depth 1 https://github.com/dotnet/skillsWrote 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/agents/dotnet/skills/build-perf)<a href="https://agentmods.dev/agents/dotnet/skills/build-perf"><img src="https://agentmods.dev/badge/agents/dotnet/skills/build-perf/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/agents/dotnet/skills/build-perf"><img src="https://agentmods.dev/badge/agents/dotnet/skills/build-perf.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 | $0.00057 | $0.01123 |
| Opus 5.5 | $0.00023 | $0.00449 |
| Sonnet 5.5 | $0.00011 | $0.00225 |
| Haiku 4.5 | $0.00006 | $0.00112 |
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 yesterday.
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 — 87 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.
- yesterday Changed · +1 lines 622f219a43d6
- 1mo ago First seen · 86 lines · 57 tokens per session scan A ad7f5870b1f9
build-perf is an agent published in the GitHub repository dotnet/skills (5,660 stars, last pushed today), licensed MIT. It adds 57 tokens to every session and 1,123 once invoked, about $0.0002 per session on Opus 5.5. 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.
Other agents, from other repositories
debugger
Diagnoses and fixes failed modules using root-cause analysis, not guessing.
loom-advisor
Read-only advisory agent for debugging and repeated failures. Spawned instead of a blind retry when an implementer has failed twice on the same task, or a bug resists straightforward diagnosis. Returns a root-cause diagnosis plus one concrete next step.
debugger
Investigate errors systematically to find root cause before attempting fixes. Gathers evidence, analyzes patterns, and forms testable hypotheses.
evolve-retrospective
Failure post-mortem agent for the Evolve Loop. Fires only on Auditor FAIL or WARN verdicts. Reads cycle artifacts and produces a structured retrospective + failure-lesson YAML files. READ-ONLY outside the lessons directory.
type-reconstructor
Dedicated struct/class reconstruction from IDA Pro decompiled binaries. Scans every function for memory access patterns, merges evidence across the module, resolves vtable and COM interface layouts, and generates compilable C++ header files with per-field confidence annotations. Use for full-module or single-class…
runtime-observer
Dynamic observation agent designed to inspect running applications, trace state transitions, log API traffic, and flag race conditions, cache states, or timing issues. Trigger with "start runtime observer", "observe live system", "trace API calls", or during characterization test validation.