awesome-copilot/skills/dotnet-mcp-builder/references/packages.md

NuGet packages and target frameworks

The 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
ModelContextProtocol.Extensions.Tasks (2.x)	Long-running task support (the MCP Tasks extension)	Production replacement for the experimental 1.4.x Tasks APIs; register via WithTasks(...)
ModelContextProtocol.Extensions.Apps (2.x)	MCP Apps — interactive UI rendered in the host	Typed [McpAppUi] attribute + .WithMcpApps() registration replacing the hand-rolled _meta wiring of 1.x; you still serve the UI as a ui:// resource, and the APIs are experimental (MCPEXP003) — see mcp-apps.md

Rule of thumb:

• New STDIO server → ModelContextProtocol + Microsoft.Extensions.Hosting.
• New HTTP server → ModelContextProtocol.AspNetCore only (it transitively pulls in everything you need).
• Pure client app → ModelContextProtocol.Core (or ModelContextProtocol if you also want hosting/DI for the client).

Versions

As of mid-2026, the stable line is 2.x (2.0.0 is current at time of writing), aligned with the MCP 2026-07-28 spec. 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0.x line was preview and has breaking differences — if you find docs or blog posts referencing 0.4/0.6, treat them as out of date. The 1.x line still compiles and interoperates, but predates the v2 changes (stateless-by-default HTTP, discovery-first negotiation, roots/sampling/logging deprecations, the Tasks/Apps extension packages) — prefer 2.x for new projects.

Upgrading 1.x → 2.0 (highlights, not exhaustive): stable v1.x APIs keep working; the deprecated capabilities (roots, sampling, logging) are now [Obsolete] with MCP9005 warnings, experimental APIs moved (the 1.4.x Tasks surface → ModelContextProtocol.Extensions.Tasks), and several behaviors flipped (HttpServerTransportOptions.Stateless now defaults to true; non-object tool results emit raw structuredContent values; Tool.inputSchema is required on deserialization). OAuth also changed at runtime — AuthorizationRedirectDelegate → ClientOAuthOptions.AuthorizationCallbackHandler, RFC 9207 issuer validation, mandatory PKCE S256 in metadata, application_type in dynamic registration — and SSE transport failures now propagate the underlying HttpRequestException/TimeoutException. Before upgrading, read the full v2.0.0 release notes.

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.