MCPSharp

What is MCPSharp?

MCPSharp is a .NET library that helps you build Model Context Protocol (MCP) servers and clients, the standardized API protocol used by AI assistants and models. It allows you to create MCP-compliant tools and functions, connect to MCP servers from C# code, and expose .NET methods as MCP endpoints using simple attributes.

How to use MCPSharp?

Install the NuGet package with dotnet add package MCPSharp. Define a class and mark methods with the [McpTool] attribute, then start the server by calling MCPServer.StartAsync("serverName", "1.0.0"). Optionally, register tools from referenced libraries using MCPServer.Register<T>().

Key features of MCPSharp

• Easy-to-use attribute-based API ([McpTool], [McpResource])
• Built-in JSON-RPC support with automatic request/response handling
• Automatic parameter validation and type conversion
• Rich documentation support through XML comments
• Dynamic tool registration with custom implementation logic
• Integration with Microsoft.Extensions.AI and Semantic Kernel

Use cases of MCPSharp

• Create tools that AI assistants like Anthropic's Claude Desktop can use
• Build MCP-compliant APIs without dealing with protocol details
• Expose existing .NET code as MCP endpoints
• Add AI capabilities to applications through standardized interfaces
• Integrate with Microsoft.Extensions.AI or Semantic Kernel without vendor lock-in

FAQ from MCPSharp

What are the runtime dependencies for MCPSharp?

MCPSharp requires any version of .NET that supports .NET Standard 2.0.

How do I define a tool in MCPSharp?

Create a class and mark a method with the [McpTool] attribute, optionally providing a name and description. Use [McpParameter] to specify parameter metadata.

Can I use MCPSharp with Semantic Kernel?

Yes. Mark methods with [KernelFunction] and [Description], then register the class with MCPServer.Register<T>(). The server will expose those methods as MCP tools.

How does MCPSharp integrate with Microsoft.Extensions.AI?

On the client side, call client.GetFunctionsAsync() to obtain a list of AIFunction objects that can be plugged into ChatOptions.Tools for any IChatClient implementation.

Are there any migration notes from previous versions?

Yes. The [McpFunction] attribute is deprecated and replaced with [McpTool]. Also, use MCPServer.Register<T>() instead of the deprecated MCPServer.RegisterTool<T>().