McpEndpointRouteBuilderExtensions.cs

using Microsoft.AspNetCore.Routing;
using Microsoft.Extensions.DependencyInjection;
using ModelContextProtocol.AspNetCore;
using System.Diagnostics.CodeAnalysis;

namespace Microsoft.AspNetCore.Builder;

/// <summary>
/// Provides extension methods for <see cref="IEndpointRouteBuilder"/> to add MCP endpoints.
/// </summary>
public static class McpEndpointRouteBuilderExtensions
{
    /// <summary>
    /// Sets up endpoints for handling MCP HTTP Streaming transport.
    /// See <see href="https://modelcontextprotocol.io/specification/2025-03-26/basic/transports#streamable-http">the protocol specification</see> for details about the Streamable HTTP transport.
    /// </summary>
    /// <param name="endpoints">The web application to attach MCP HTTP endpoints.</param>
    /// <param name="pattern">The route pattern prefix to map to.</param>
    /// <returns>Returns a builder for configuring additional endpoint conventions like authorization policies.</returns>
    public static IEndpointConventionBuilder MapMcp(this IEndpointRouteBuilder endpoints, [StringSyntax("Route")] string pattern = "")
    {
        var handler = endpoints.ServiceProvider.GetService<StreamableHttpHandler>() ??
            throw new InvalidOperationException("You must call WithHttpTransport(). Unable to find required services. Call builder.Services.AddMcpServer().WithHttpTransport() in application startup code.");

        var routeGroup = endpoints.MapGroup(pattern);
        routeGroup.MapGet("", handler.HandleRequestAsync);
        routeGroup.MapGet("/sse", handler.HandleRequestAsync);
        routeGroup.MapPost("/message", handler.HandleRequestAsync);
        return routeGroup;
    }
}