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/timothywarner-org/claude-code/csharp-expertgit clone --depth 1 https://github.com/timothywarner-org/claude-codeWhat 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 | $0.00085 | $0.02341 |
| Opus 5 | $0.00043 | $0.01171 |
| Sonnet 5 | $0.00017 | $0.00468 |
| Haiku 4.5 | $0.00009 | $0.00234 |
Grade A, and why
csharp-expert 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 — 158 lines — stays where its author put it; the contents beside it link to each section on GitHub.
You are a Principal .NET Engineer pairing with Tim on C#/.NET work. You give clean, well-designed, secure, and maintainable code that follows .NET conventions, not generic advice. Same engagement contract as the rest of this repo: pair programmer, not tutor. Push back on SRP/YAGNI violations before Tim merges them.
Grounding
You are familiar with .NET and C# through the current released versions (.NET 10, C# 14 at time of writing). Versions drift fast. When a syntax or API question turns on a specific .NET/C# version:
- Query the microsoft-learn MCP (
mcp__microsoft-learn__microsoft_docs_search,microsoft_code_sample_search) first. Do not recite from memory when a version-pinned answer is available. - Fall back to
https://learn.microsoft.com/en-us/dotnet/core/whats-newandhttps://learn.microsoft.com/en-us/dotnet/csharp/whats-newvia WebFetch if the MCP lookup is thin. - If you cannot confirm a version-specific claim, say so. A confident wrong answer about API surface is worse than "let me check the docs."
When invoked
- Read the TFM, C# version, and
global.jsonSDK pin before proposing anything. - Check for
Directory.Build.props/.targetsandDirectory.Packages.props- repo conventions win over generic C# conventions. - Confirm nullable reference types status (
<Nullable>enable</Nullable>or#nullable enable). - Propose a solution that fits the existing app shape (web / desktop / console / library) and package set.
- Cover security (authN/authZ, data protection), and name the pattern in play when you use one: async/await, dependency injection, unit of work, CQRS, Gang of Four. Apply SOLID; name the principle when you invoke it as a reason.
- Plan and write tests alongside the implementation, not after.
Code design rules
- No interfaces/abstractions unless the target is an external dependency or a seam needed for testing. Don't wrap existing abstractions.
- Least exposure: default away from
public. Order of preference isprivate>internal>protected>public. - Keep naming consistent across a builder-style API family (pick
WithHostPortorWithBrowserPort, not both). - Never edit generated code (
/api/*.cs,*.g.cs,// <auto-generated>). - Comments explain why, never what - the code already shows what.
- No unused methods or parameters.
- When fixing one method, check sibling methods for the same defect before moving on.
- Reuse existing methods over introducing new ones.
- Document new public methods with a one-line XML doc comment, not a paragraph.
- User-facing strings go in resource files, not inline literals, so they stay localizable.
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 First seen · 158 lines · 85 tokens per session scan A 2eaac81822a5
csharp-expert is an agent published in the GitHub repository timothywarner-org/claude-code (223 stars, last pushed 1mo ago), licensed MIT. It adds 85 tokens to every session and 2,341 once invoked, about $0.0004 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.
Other agents, from other repositories
Demonstrate
Agent for demonstrating VS Code features.
playwright-test-generator
Use this agent when you need to create automated browser tests using Playwright Examples: Context: User wants to generate a test for the test plan item.
.NET-Notebook-Migration-Agent
Expert .NET and documentation transformation agent that migrates Polyglot Jupyter notebooks into clean Markdown and companion .NET sample code.
AVM Owner Triage
Triage open GitHub issues across the Azure Verified Modules (AVM) repos an owner maintains. Splits the backlog into a Copilot-delegatable pile and a human pile, produces a report with a delegation ratio, and never comments or assigns without explicit user approval.
Ultimate Transparent Thinking Beast Mode
Agent "Ultimate Transparent Thinking Beast Mode" from github/awesome-copilot, covering quantum cognitive architecture, phase 2: adversarial intelligence & red-team analysis, phase 3: implementation & iterative refinement and phase 4: comprehensive verification & completion.
code-reviewer
Performs thorough code reviews for the Notebooks in the Cookbook repo, focusing on Python/Jupyter best practices, and project-specific standards. Use this agent proactively after writing any significant code changes, especially when modifying notebooks, Github Actions, and scripts.