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 SebastienDegodez/copilot-instructions --skill creating-dotnet-mcp-serversgit clone --depth 1 https://github.com/SebastienDegodez/copilot-instructionsWrote 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/sebastiendegodez/copilot-instructions/creating-dotnet-mcp-servers)<a href="https://agentmods.dev/skills/sebastiendegodez/copilot-instructions/creating-dotnet-mcp-servers"><img src="https://agentmods.dev/badge/skills/sebastiendegodez/copilot-instructions/creating-dotnet-mcp-servers/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/sebastiendegodez/copilot-instructions/creating-dotnet-mcp-servers"><img src="https://agentmods.dev/badge/skills/sebastiendegodez/copilot-instructions/creating-dotnet-mcp-servers.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00043 | $0.01209 |
| Opus 5.5 | $0.00017 | $0.00484 |
| Sonnet 5.5 | $0.00009 | $0.00242 |
| Haiku 4.5 | $0.00004 | $0.00121 |
Grade A, and why
creating-dotnet-mcp-servers 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 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.
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 — 145 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Creating .NET MCP Servers
Build production-ready Model Context Protocol (MCP) servers in .NET with AOT compatibility.
Core principle: MCP servers expose tools via standardized protocol using attribute-based registration and explicit JSON serialization contexts for AOT.
When to Use
graph TD
A[Need to build server?] -->|Yes| B[Using .NET?]
B -->|Yes| C[MCP Protocol?]
C -->|Yes| D[✅ Use this skill]
C -->|No| E[❌ Use REST/gRPC guide]
B -->|No| F[❌ See Python/TS MCP docs]
A -->|No| G[❌ Skip]
Use this skill when:
- Building new MCP server in .NET
- Configuring SSE or stdio transport
- Enabling AOT compilation
- Need testing or error handling patterns
Not for: Non-.NET MCP, client-side integration, generic APIs
Quick Reference
| Task | Implementation |
|---|---|
| Install packages | dotnet add package ModelContextProtocol + ModelContextProtocol.AspNetCore |
| Mark tool class | [McpServerToolType] |
| Mark tool method | [McpServerTool(Name = "ToolName"), Description("...")] |
| Parameter description | [Description("param description")] string param |
| Register server | services.AddMcpServer().WithHttpTransport().WithTools<T>() |
| Map endpoints | app.MapMcp() (exposes /sse) |
| AOT serialization | Create JsonSerializerContext with [JsonSerializable] |
| Test transport | Use SseClientTransport + McpClientFactory |
Basic Setup
1. Install Packages
dotnet add package ModelContextProtocol --version 0.3.0-preview.1
dotnet add package ModelContextProtocol.AspNetCore --version 0.3.0-preview.1
# For testing (optional)
dotnet add package ModelContextProtocol.Client --version 0.3.0-preview.1
2. Enable AOT
Project configuration:
<PropertyGroup>
<PublishAot>true</PublishAot>
<JsonSerializerIsReflectionEnabledByDefault>false</JsonSerializerIsReflectionEnabledByDefault>
</PropertyGroup>
JSON serialization context:
[JsonSerializable(typeof(PackageMetadata))]
[JsonSerializable(typeof(IEnumerable<PackageMetadata>))]
public partial class McpJsonContext : JsonSerializerContext { }
What ships with it
3 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 · 145 lines · 43 tokens per session scan A cb7e3780c38f
creating-dotnet-mcp-servers is a skill published in the GitHub repository SebastienDegodez/copilot-instructions (199 stars, last pushed 19d ago), licensed Apache-2.0. It adds 43 tokens to every session and 1,209 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.
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