csharp-sdk/src/ModelContextProtocol/Configuration/McpServerBuilderExtensions.cs

using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using ModelContextProtocol.Hosting;
using ModelContextProtocol.Protocol.Transport;
using ModelContextProtocol.Protocol.Types;
using ModelContextProtocol.Server;
using ModelContextProtocol.Utils;
using System.Diagnostics.CodeAnalysis;
using System.Reflection;

namespace Microsoft.Extensions.DependencyInjection;

/// <summary>
/// Provides methods for configuring MCP servers via dependency injection.
/// </summary>
public static partial class McpServerBuilderExtensions
{
    #region WithTools
    private const string WithToolsRequiresUnreferencedCodeMessage =
        $"The non-generic {nameof(WithTools)} and {nameof(WithToolsFromAssembly)} methods require dynamic lookup of method metadata" +
        $"and may not work in Native AOT. Use the generic {nameof(WithTools)} method instead.";

    /// <summary>Adds <see cref="McpServerTool"/> instances to the service collection backing <paramref name="builder"/>.</summary>
    /// <typeparam name="TToolType">The tool type.</typeparam>
    /// <param name="builder">The builder instance.</param>
    /// <exception cref="ArgumentNullException"><paramref name="builder"/> is <see langword="null"/>.</exception>
    /// <remarks>
    /// This method discovers all instance and static methods (public and non-public) on the specified <typeparamref name="TToolType"/>
    /// type, where the methods are attributed as <see cref="McpServerToolAttribute"/>, and adds an <see cref="McpServerTool"/>
    /// instance for each. For instance methods, an instance will be constructed for each invocation of the tool.
    /// </remarks>
    public static IMcpServerBuilder WithTools<[DynamicallyAccessedMembers(
        DynamicallyAccessedMemberTypes.PublicMethods |
        DynamicallyAccessedMemberTypes.NonPublicMethods |
        DynamicallyAccessedMemberTypes.PublicConstructors)] TToolType>(
        this IMcpServerBuilder builder)
    {
        Throw.IfNull(builder);

        foreach (var toolMethod in typeof(TToolType).GetMethods(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.Instance))
        {
            if (toolMethod.GetCustomAttribute<McpServerToolAttribute>() is not null)
            {
                builder.Services.AddSingleton((Func<IServiceProvider, McpServerTool>)(toolMethod.IsStatic ?
                    services => McpServerTool.Create(toolMethod, options: new() { Services = services }) :
                    services => McpServerTool.Create(toolMethod, typeof(TToolType), new() { Services = services })));
            }
        }

        return builder;
    }

    /// <summary>Adds <see cref="McpServerTool"/> instances to the service collection backing <paramref name="builder"/>.</summary>
    /// <param name="builder">The builder instance.</param>
    /// <param name="toolTypes">Types with marked methods to add as tools to the server.</param>
    /// <exception cref="ArgumentNullException"><paramref name="builder"/> is <see langword="null"/>.</exception>
    /// <exception cref="ArgumentNullException"><paramref name="toolTypes"/> is <see langword="null"/>.</exception>
    /// <remarks>
    /// This method discovers all instance and static methods (public and non-public) on the specified <paramref name="toolTypes"/>
    /// types, where the methods are attributed as <see cref="McpServerToolAttribute"/>, and adds an <see cref="McpServerTool"/>
    /// instance for each. For instance methods, an instance will be constructed for each invocation of the tool.
    /// </remarks>
    [RequiresUnreferencedCode(WithToolsRequiresUnreferencedCodeMessage)]
    public static IMcpServerBuilder WithTools(this IMcpServerBuilder builder, params IEnumerable<Type> toolTypes)
    {
        Throw.IfNull(builder);
        Throw.IfNull(toolTypes);

        foreach (var toolType in toolTypes)
        {
            if (toolType is not null)
            {
                foreach (var toolMethod in toolType.GetMethods(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.Instance))
                {
                    if (toolMethod.GetCustomAttribute<McpServerToolAttribute>() is not null)
                    {
                        builder.Services.AddSingleton((Func<IServiceProvider, McpServerTool>)(toolMethod.IsStatic ?
                            services => McpServerTool.Create(toolMethod, options: new() { Services = services }) :
                            services => McpServerTool.Create(toolMethod, toolType, new() { Services = services })));
                    }
                }
            }
        }

        return builder;
    }

    /// <summary>
    /// Adds types marked with the <see cref="McpServerToolTypeAttribute"/> attribute from the given assembly as tools to the server.
    /// </summary>
    /// <param name="builder">The builder instance.</param>
    /// <param name="toolAssembly">The assembly to load the types from. Null to get the current assembly</param>
    /// <exception cref="ArgumentNullException"><paramref name="builder"/> is <see langword="null"/>.</exception>
    [RequiresUnreferencedCode(WithToolsRequiresUnreferencedCodeMessage)]
    public static IMcpServerBuilder WithToolsFromAssembly(this IMcpServerBuilder builder, Assembly? toolAssembly = null)
    {
        Throw.IfNull(builder);

        toolAssembly ??= Assembly.GetCallingAssembly();

        return builder.WithTools(
            from t in toolAssembly.GetTypes()
            where t.GetCustomAttribute<McpServerToolTypeAttribute>() is not null
            select t);
    }
    #endregion

    #region WithPrompts
    private const string WithPromptsRequiresUnreferencedCodeMessage =
        $"The non-generic {nameof(WithPrompts)} and {nameof(WithPromptsFromAssembly)} methods require dynamic lookup of method metadata" +
        $"and may not work in Native AOT. Use the generic {nameof(WithPrompts)} method instead.";

    /// <summary>Adds <see cref="McpServerPrompt"/> instances to the service collection backing <paramref name="builder"/>.</summary>
    /// <typeparam name="TPromptType">The prompt type.</typeparam>
    /// <param name="builder">The builder instance.</param>
    /// <exception cref="ArgumentNullException"><paramref name="builder"/> is <see langword="null"/>.</exception>
    /// <remarks>
    /// This method discovers all instance and static methods (public and non-public) on the specified <typeparamref name="TPromptType"/>
    /// type, where the methods are attributed as <see cref="McpServerPromptAttribute"/>, and adds an <see cref="McpServerPrompt"/>
    /// instance for each. For instance methods, an instance will be constructed for each invocation of the prompt.
    /// </remarks>
    public static IMcpServerBuilder WithPrompts<[DynamicallyAccessedMembers(
        DynamicallyAccessedMemberTypes.PublicMethods |
        DynamicallyAccessedMemberTypes.NonPublicMethods |
        DynamicallyAccessedMemberTypes.PublicConstructors)] TPromptType>(
        this IMcpServerBuilder builder)
    {
        Throw.IfNull(builder);

        foreach (var promptMethod in typeof(TPromptType).GetMethods(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.Instance))
        {
            if (promptMethod.GetCustomAttribute<McpServerPromptAttribute>() is not null)
            {
                builder.Services.AddSingleton((Func<IServiceProvider, McpServerPrompt>)(promptMethod.IsStatic ?
                    services => McpServerPrompt.Create(promptMethod, options: new() { Services = services }) :
                    services => McpServerPrompt.Create(promptMethod, typeof(TPromptType), new() { Services = services })));
            }
        }

        return builder;
    }

    /// <summary>Adds <see cref="McpServerPrompt"/> instances to the service collection backing <paramref name="builder"/>.</summary>
    /// <param name="builder">The builder instance.</param>
    /// <param name="promptTypes">Types with marked methods to add as prompts to the server.</param>
    /// <exception cref="ArgumentNullException"><paramref name="builder"/> is <see langword="null"/>.</exception>
    /// <exception cref="ArgumentNullException"><paramref name="promptTypes"/> is <see langword="null"/>.</exception>
    /// <remarks>
    /// This method discovers all instance and static methods (public and non-public) on the specified <paramref name="promptTypes"/>
    /// types, where the methods are attributed as <see cref="McpServerPromptAttribute"/>, and adds an <see cref="McpServerPrompt"/>
    /// instance for each. For instance methods, an instance will be constructed for each invocation of the prompt.
    /// </remarks>
    [RequiresUnreferencedCode(WithPromptsRequiresUnreferencedCodeMessage)]
    public static IMcpServerBuilder WithPrompts(this IMcpServerBuilder builder, params IEnumerable<Type> promptTypes)
    {
        Throw.IfNull(builder);
        Throw.IfNull(promptTypes);

        foreach (var promptType in promptTypes)
        {
            if (promptType is not null)
            {
                foreach (var promptMethod in promptType.GetMethods(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.Instance))
                {
                    if (promptMethod.GetCustomAttribute<McpServerPromptAttribute>() is not null)
                    {
                        builder.Services.AddSingleton((Func<IServiceProvider, McpServerPrompt>)(promptMethod.IsStatic ?
                            services => McpServerPrompt.Create(promptMethod, options: new() { Services = services }) :
                            services => McpServerPrompt.Create(promptMethod, promptType, new() { Services = services })));
                    }
                }
            }
        }

        return builder;
    }

    /// <summary>
    /// Adds types marked with the <see cref="McpServerToolTypeAttribute"/> attribute from the given assembly as prompts to the server.
    /// </summary>
    /// <param name="builder">The builder instance.</param>
    /// <param name="promptAssembly">The assembly to load the types from. Null to get the current assembly</param>
    /// <exception cref="ArgumentNullException"><paramref name="builder"/> is <see langword="null"/>.</exception>
    [RequiresUnreferencedCode(WithPromptsRequiresUnreferencedCodeMessage)]
    public static IMcpServerBuilder WithPromptsFromAssembly(this IMcpServerBuilder builder, Assembly? promptAssembly = null)
    {
        Throw.IfNull(builder);

        promptAssembly ??= Assembly.GetCallingAssembly();

        return builder.WithPrompts(
            from t in promptAssembly.GetTypes()
            where t.GetCustomAttribute<McpServerToolTypeAttribute>() is not null
            select t);
    }
    #endregion

    #region Handlers
    /// <summary>
    /// Sets the handler for list resource templates requests.
    /// </summary>
    /// <param name="builder">The builder instance.</param>
    /// <param name="handler">The handler.</param>
    public static IMcpServerBuilder WithListResourceTemplatesHandler(this IMcpServerBuilder builder, Func<RequestContext<ListResourceTemplatesRequestParams>, CancellationToken, Task<ListResourceTemplatesResult>> handler)
    {
        Throw.IfNull(builder);

        builder.Services.Configure<McpServerHandlers>(s => s.ListResourceTemplatesHandler = handler);
        return builder;
    }

    /// <summary>
    /// Sets the handler for list tools requests.
    /// </summary>
    /// <param name="builder">The builder instance.</param>
    /// <param name="handler">The handler.</param>
    public static IMcpServerBuilder WithListToolsHandler(this IMcpServerBuilder builder, Func<RequestContext<ListToolsRequestParams>, CancellationToken, Task<ListToolsResult>> handler)
    {
        Throw.IfNull(builder);

        builder.Services.Configure<McpServerHandlers>(s => s.ListToolsHandler = handler);
        return builder;
    }

    /// <summary>
    /// Sets the handler for call tool requests.
    /// </summary>
    /// <param name="builder">The builder instance.</param>
    /// <param name="handler">The handler.</param>
    public static IMcpServerBuilder WithCallToolHandler(this IMcpServerBuilder builder, Func<RequestContext<CallToolRequestParams>, CancellationToken, Task<CallToolResponse>> handler)
    {
        Throw.IfNull(builder);

        builder.Services.Configure<McpServerHandlers>(s => s.CallToolHandler = handler);
        return builder;
    }

    /// <summary>
    /// Sets the handler for list prompts requests.
    /// </summary>
    /// <param name="builder">The builder instance.</param>
    /// <param name="handler">The handler.</param>
    public static IMcpServerBuilder WithListPromptsHandler(this IMcpServerBuilder builder, Func<RequestContext<ListPromptsRequestParams>, CancellationToken, Task<ListPromptsResult>> handler)
    {
        Throw.IfNull(builder);

        builder.Services.Configure<McpServerHandlers>(s => s.ListPromptsHandler = handler);
        return builder;
    }

    /// <summary>
    /// Sets the handler for get prompt requests.
    /// </summary>
    /// <param name="builder">The builder instance.</param>
    /// <param name="handler">The handler.</param>
    public static IMcpServerBuilder WithGetPromptHandler(this IMcpServerBuilder builder, Func<RequestContext<GetPromptRequestParams>, CancellationToken, Task<GetPromptResult>> handler)
    {
        Throw.IfNull(builder);

        builder.Services.Configure<McpServerHandlers>(s => s.GetPromptHandler = handler);
        return builder;
    }

    /// <summary>
    /// Sets the handler for list resources requests.
    /// </summary>
    /// <param name="builder">The builder instance.</param>
    /// <param name="handler">The handler.</param>
    public static IMcpServerBuilder WithListResourcesHandler(this IMcpServerBuilder builder, Func<RequestContext<ListResourcesRequestParams>, CancellationToken, Task<ListResourcesResult>> handler)
    {
        Throw.IfNull(builder);

        builder.Services.Configure<McpServerHandlers>(s => s.ListResourcesHandler = handler);
        return builder;
    }

    /// <summary>
    /// Sets the handler for read resources requests.
    /// </summary>
    /// <param name="builder">The builder instance.</param>
    /// <param name="handler">The handler.</param>
    public static IMcpServerBuilder WithReadResourceHandler(this IMcpServerBuilder builder, Func<RequestContext<ReadResourceRequestParams>, CancellationToken, Task<ReadResourceResult>> handler)
    {
        Throw.IfNull(builder);

        builder.Services.Configure<McpServerHandlers>(s => s.ReadResourceHandler = handler);
        return builder;
    }

    /// <summary>
    /// Sets the handler for get completion requests.
    /// </summary>
    /// <param name="builder">The builder instance.</param>
    /// <param name="handler">The handler.</param>
    public static IMcpServerBuilder WithGetCompletionHandler(this IMcpServerBuilder builder, Func<RequestContext<CompleteRequestParams>, CancellationToken, Task<CompleteResult>> handler)
    {
        Throw.IfNull(builder);

        builder.Services.Configure<McpServerHandlers>(s => s.GetCompletionHandler = handler);
        return builder;
    }

    /// <summary>
    /// Sets the handler for subscribe to resources messages.
    /// </summary>
    /// <param name="builder">The builder instance.</param>
    /// <param name="handler">The handler.</param>
    public static IMcpServerBuilder WithSubscribeToResourcesHandler(this IMcpServerBuilder builder, Func<RequestContext<SubscribeRequestParams>, CancellationToken, Task<EmptyResult>> handler)
    {
        Throw.IfNull(builder);

        builder.Services.Configure<McpServerHandlers>(s => s.SubscribeToResourcesHandler = handler);
        return builder;
    }

    /// <summary>
    /// Sets or sets the handler for subscribe to resources messages.
    /// </summary>
    /// <param name="builder">The builder instance.</param>
    /// <param name="handler">The handler.</param>
    public static IMcpServerBuilder WithUnsubscribeFromResourcesHandler(this IMcpServerBuilder builder, Func<RequestContext<UnsubscribeRequestParams>, CancellationToken, Task<EmptyResult>> handler)
    {
        Throw.IfNull(builder);

        builder.Services.Configure<McpServerHandlers>(s => s.UnsubscribeFromResourcesHandler = handler);
        return builder;
    }
    #endregion

    #region Transports
    /// <summary>
    /// Adds a server transport that uses stdin/stdout for communication.
    /// </summary>
    /// <param name="builder">The builder instance.</param>
    public static IMcpServerBuilder WithStdioServerTransport(this IMcpServerBuilder builder)
    {
        Throw.IfNull(builder);

        builder.Services.AddSingleton<ITransport, StdioServerTransport>();
        builder.Services.AddHostedService<StdioMcpServerHostedService>();

        builder.Services.AddSingleton(services =>
        {
            ITransport serverTransport = services.GetRequiredService<ITransport>();
            IOptions<McpServerOptions> options = services.GetRequiredService<IOptions<McpServerOptions>>();
            ILoggerFactory? loggerFactory = services.GetService<ILoggerFactory>();

            return McpServerFactory.Create(serverTransport, options.Value, loggerFactory, services);
        });

        return builder;
    }
    #endregion
}