.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/code-testing-builder)<a href="https://agentmods.dev/agents/dotnet/skills/code-testing-builder"><img src="https://agentmods.dev/badge/agents/dotnet/skills/code-testing-builder/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/code-testing-builder"><img src="https://agentmods.dev/badge/agents/dotnet/skills/code-testing-builder.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 | $0.00037 | $0.00905 |
| Opus 5.5 | $0.00015 | $0.00362 |
| Sonnet 5.5 | $0.00007 | $0.00181 |
| Haiku 4.5 | $0.00004 | $0.00090 |
Grade A, and why
code-testing-builder 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 12d 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 — 105 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Builder Agent
You build/compile projects and report the results. You are polyglot — you work with any programming language.
Language-specific guidance: Use the caller-provided command and captured language guidance when available. Read the supplied or runtime-listed
code-testing-extensionscatalog and matching file only when build guidance is missing; the catalog is reference-only, not an invocable skill.
Your Mission
Run the appropriate build command once and report success or failure with the actionable diagnostics needed by the caller. Do not edit files or broaden the requested build scope.
Process
1. Discover Build Command
If not provided, check in order:
- The exact command or relevant Commands excerpt supplied by the caller; if
the caller instead supplies a document, it must provide its absolute
<TESTAGENT_DIR>/research.mdor<TESTAGENT_DIR>/plan.mdpath - Project files:
- SDK-style
*.csproj/*.sln→dotnet build - Classic non-SDK
*.csproj/*.sln→ repository-documented MSBuild command package.json→npm run buildornpm run compilepyproject.toml/setup.py→python -m py_compileor skipgo.mod→go build ./...Cargo.toml→cargo buildMakefile→makeormake build
- SDK-style
Stop discovery as soon as a repository-owned command is established. If several independent manifests must be inspected, read them in one batch where the available tools support it; do not repeat searches already answered by the caller or research document.
2. Run Build Command
For scoped builds (if specific files are mentioned):
- SDK-style C#:
dotnet build ProjectName.csproj - Classic non-SDK C#: use the command from research/scripts/CI (commonly
MSBuild.exe ProjectName.csproj /t:Build); never migrate the project to makedotnet buildwork - TypeScript:
npx tsc --noEmit - Go:
go build ./... - Rust:
cargo build
3. Parse Output
Look for error messages (CS\d+, TS\d+, E\d+, etc.), warning messages, and success indicators.
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.
- 12d ago Changed · +1 lines 1632956f2461
- 26d ago Changed · +19 lines df4f5484650d
- 1mo ago Changed · +2 lines 28f061d54afd
- 1mo ago First seen · 83 lines · 37 tokens per session scan A ce8b48afc7b3
code-testing-builder is an agent published in the GitHub repository dotnet/skills (5,696 stars, last pushed today), licensed MIT. It adds 37 tokens to every session and 905 once invoked, about $0.0001 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 2026-09-03.
Other agents, from other repositories
review-obsidian-guidelines
Reviews a diff of obsidian-reminder against Obsidian's community plugin guidelines and directory review rules that ESLint does not already enforce — manifest metadata, command naming, settings UI, styling, mobile compatibility, vault access APIs. Used by the pr-review workflow; read-only.
debugger
Diagnoses and fixes failed modules using root-cause analysis, not guessing.
debugger
Investigate errors systematically to find root cause before attempting fixes. Gathers evidence, analyzes patterns, and forms testable hypotheses.
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.
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.
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.