Adrien Clerbois
2c275f2ef9
* feat(skills): add dotnet-mcp-builder, deprecate csharp-mcp-server-generator Adds a comprehensive skill for building MCP (Model Context Protocol) servers in C#/.NET against the official ModelContextProtocol 1.x NuGet packages. Covers both transports (STDIO, Streamable HTTP — SSE is deprecated) and every primitive in the current MCP spec (2025-11-25): tools, prompts, resources, elicitation (form + URL mode), sampling, roots, completions, logging, and MCP Apps. Includes a thin .NET MCP client reference and testing guidance (MCP Inspector + in-memory transport for unit tests). Steers the model toward the current stable 1.x packages instead of the 0.x previews it tends to pin by default, and enforces the STDIO stdout/stderr trap. Also deprecates the existing csharp-mcp-server-generator skill, which predates ModelContextProtocol 1.0 and only covered a subset of the current spec. Its SKILL.md now redirects users to dotnet-mcp-builder so existing install URLs keep working without surprises. * fix: address PR review from aaronpowell - Delete csharp-mcp-server-generator skill (rather than deprecating it) - Update mcp-apps.md pitfalls section to reference .NET Tool.Meta type instead of the serialized _meta JSON property names - Rebuild docs/README.skills.md Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> * chore: remove C# MCP development plugin files * chore: remove csharp-mcp-development plugin entry from marketplace --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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NuGet packages and target frameworks
The three official packages
All packages live under the ModelContextProtocol NuGet profile. The official C# SDK repo is modelcontextprotocol/csharp-sdk, maintained jointly by the MCP project and Microsoft.
| Package | When to use it | Brings in |
|---|---|---|
ModelContextProtocol |
Default for STDIO servers and most projects | Core + Microsoft.Extensions.Hosting integration, attribute discovery (AddMcpServer, WithToolsFromAssembly, etc.) |
ModelContextProtocol.AspNetCore |
HTTP (Streamable) servers hosted in ASP.NET Core | The above + WithHttpTransport and MapMcp |
ModelContextProtocol.Core |
Pure clients, custom hosts, low-level scenarios where you don't want the Microsoft.Extensions.* dependencies |
Just the protocol + transports + low-level McpServer.Create / McpClient.CreateAsync |
Rule of thumb:
- New STDIO server →
ModelContextProtocol+Microsoft.Extensions.Hosting. - New HTTP server →
ModelContextProtocol.AspNetCoreonly (it transitively pulls in everything you need). - Pure client app →
ModelContextProtocol.Core(orModelContextProtocolif you also want hosting/DI for the client).
Versions
As of 2026, the stable line is 1.x (1.2.0 is current at time of writing). The 0.x line was preview and has breaking differences — if you find docs or blog posts referencing 0.4/0.6, treat them as out of date.
To check the latest:
dotnet search ModelContextProtocol --prerelease
Target frameworks
The SDK targets .NET 8.0 and netstandard2.0. That means it runs on:
- .NET 8 (LTS)
- .NET 9
- .NET 10 (current LTS — recommended for new projects)
- .NET Framework 4.6.2+ via netstandard2.0 (rare; only for legacy hosts)
For HTTP servers you specifically need a TFM that supports ASP.NET Core (so .NET 8/9/10).
Project setup commands
STDIO server
dotnet new console -n MyMcpServer -f net10.0
cd MyMcpServer
dotnet add package ModelContextProtocol
dotnet add package Microsoft.Extensions.Hosting
HTTP (Streamable) server
dotnet new web -n MyMcpServer -f net10.0
cd MyMcpServer
dotnet add package ModelContextProtocol.AspNetCore
(dotnet new web gives you a minimal ASP.NET Core project — exactly what MapMcp needs.)
Client
dotnet new console -n MyMcpClient -f net10.0
cd MyMcpClient
dotnet add package ModelContextProtocol.Core
Optional but commonly useful
| Package | Why |
|---|---|
Microsoft.Extensions.AI |
Provides IChatClient, ChatMessage, ChatRole, ChatOptions — the abstractions used by AsSamplingChatClient() and by prompt return types. |
Microsoft.Extensions.AI.Abstractions |
Pulled in transitively but worth knowing about for types like DataContent, TextContent. |
OpenTelemetry.Extensions.Hosting |
The SDK emits OTel traces and metrics for tool calls — wire them up if the user has an observability story. |
What about dnx?
Newer Microsoft examples sometimes show launching servers via dnx PackageName --version 1.2.3. That's a valid distribution model: publish your server as a NuGet package and let users run it without cloning. It's orthogonal to how the server itself is built — keep your code identical and just change the launch command.