feat: Create an MCP server

Directory.Packages.props

@@ -7,10 +7,14 @@
     <PackageVersion Include="Microsoft.CodeAnalysis.Common" Version="4.14.0" />
     <PackageVersion Include="Microsoft.CodeAnalysis.CSharp" Version="4.14.0" />
     <PackageVersion Include="Microsoft.Extensions.Hosting" Version="9.0.7" />
+    <PackageVersion Include="Microsoft.Extensions.Http.Resilience" Version="9.7.0" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
     <PackageVersion Include="Microsoft.OpenApi.YamlReader" Version="2.0.0" />
     <PackageVersion Include="Microsoft.OpenApi" Version="2.0.0" />
     <PackageVersion Include="Microsoft.SourceLink.GitHub" Version="8.0.0" />
+    <PackageVersion Include="Microsoft.VisualStudio.Azure.Containers.Tools.Targets" Version="1.22.1" />
+    <PackageVersion Include="ModelContextProtocol" Version="0.3.0-preview.3" />
+    <PackageVersion Include="ModelContextProtocol.AspNetCore" Version="0.3.0-preview.3" />
     <PackageVersion Include="NSubstitute" Version="5.1.0" />
     <PackageVersion Include="PolySharp" Version="1.15.0" />
     <PackageVersion Include="SharpYaml" Version="2.1.3" />
@@ -25,6 +29,12 @@
     <PackageVersion Include="System.Text.Encodings.Web" Version="9.0.7" />
     <PackageVersion Include="System.Text.Json" Version="9.0.7" />
     <PackageVersion Include="System.Threading.Tasks.Extensions" Version="4.6.3" />
+    <PackageVersion Include="OpenTelemetry" Version="1.12.0" />
+    <PackageVersion Include="OpenTelemetry.Exporter.InMemory" Version="1.12.0" />
+    <PackageVersion Include="OpenTelemetry.Exporter.OpenTelemetryProtocol" Version="1.12.0" />
+    <PackageVersion Include="OpenTelemetry.Instrumentation.Http" Version="1.12.0" />
+    <PackageVersion Include="OpenTelemetry.Extensions.Hosting" Version="1.12.0" />
+    <PackageVersion Include="OpenTelemetry.Instrumentation.AspNetCore" Version="1.12.0" />
     <PackageVersion Include="xunit.runner.visualstudio" Version="3.1.3" />
     <PackageVersion Include="xunit" Version="2.9.3" />
   </ItemGroup>

OpenApi.Client.sln

@@ -27,6 +27,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "OpenApi.Client.SourceGenera
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "OpenApi.Client.Cli.UnitTests", "tests\OpenApi.Client.Cli.UnitTests\OpenApi.Client.Cli.UnitTests.csproj", "{0C407F0F-BE50-4850-B695-FE1C0910E8BB}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "OpenApi.Client.Mcp", "src\OpenApi.Client.Mcp\OpenApi.Client.Mcp.csproj", "{BA946406-F267-4996-8769-E5B607E18CB4}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -53,6 +55,10 @@ Global
 		{0C407F0F-BE50-4850-B695-FE1C0910E8BB}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{0C407F0F-BE50-4850-B695-FE1C0910E8BB}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{0C407F0F-BE50-4850-B695-FE1C0910E8BB}.Release|Any CPU.Build.0 = Release|Any CPU
+		{BA946406-F267-4996-8769-E5B607E18CB4}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{BA946406-F267-4996-8769-E5B607E18CB4}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{BA946406-F267-4996-8769-E5B607E18CB4}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{BA946406-F267-4996-8769-E5B607E18CB4}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

src/OpenApi.Client.Mcp/Configuration/McpMode.cs

@@ -0,0 +1,13 @@
+// This Source Code Form is subject to the terms of the MIT License.
+// If a copy of the MIT was not distributed with this file, You can obtain one at https://opensource.org/licenses/MIT.
+// Copyright (C) Leszek Pomianowski and OpenAPI Client Contributors.
+// All Rights Reserved.
+
+namespace OpenApi.Client.Mcp.Configuration;
+
+internal enum McpMode
+{
+    Stdio,
+    Http,
+    Both,
+}

src/OpenApi.Client.Mcp/Configuration/ServerOptions.cs

@@ -0,0 +1,11 @@
+// This Source Code Form is subject to the terms of the MIT License.
+// If a copy of the MIT was not distributed with this file, You can obtain one at https://opensource.org/licenses/MIT.
+// Copyright (C) Leszek Pomianowski and OpenAPI Client Contributors.
+// All Rights Reserved.
+
+namespace OpenApi.Client.Mcp.Configuration;
+
+internal sealed class ServerOptions
+{
+    public McpMode Mode { get; set; } = McpMode.Stdio;
+}

src/OpenApi.Client.Mcp/Dockerfile

@@ -0,0 +1,16 @@
+FROM mcr.microsoft.com/dotnet/sdk:9.0 AS build
+
+WORKDIR /src
+COPY . .
+
+RUN find . -type f -name 'appsettings.*.json' ! -name 'appsettings.json' -exec rm -f {} +
+RUN find . -name 'launchSettings.json' -exec rm -f {} +
+
+RUN dotnet publish "src/OpenApi.Client.Mcp/OpenApi.Client.Mcp.csproj" -c Release -o /app/ --nologo
+
+FROM mcr.microsoft.com/dotnet/runtime:9.0 AS final
+
+WORKDIR /app
+COPY --from=build /app/ .
+
+ENTRYPOINT ["dotnet", "./OpenApi.Client.Mcp.dll"]

src/OpenApi.Client.Mcp/GlobalUsings.cs

@@ -0,0 +1,24 @@
+// This Source Code Form is subject to the terms of the MIT License.
+// If a copy of the MIT was not distributed with this file, You can obtain one at https://opensource.org/licenses/MIT.
+// Copyright (C) Leszek Pomianowski and OpenAPI Client Contributors.
+// All Rights Reserved.
+
+global using Microsoft.AspNetCore.Builder;
+global using Microsoft.CodeAnalysis;
+global using Microsoft.Extensions.Configuration;
+global using Microsoft.Extensions.DependencyInjection;
+global using Microsoft.Extensions.Logging;
+global using OpenApi.Client.Mcp.Configuration;
+global using OpenApi.Client.Mcp.Services;
+global using OpenApi.Client.Mcp.Tools;
+global using OpenTelemetry;
+global using OpenTelemetry.Metrics;
+global using OpenTelemetry.Trace;
+global using System;
+global using System.Collections.Generic;
+global using System.ComponentModel;
+global using System.IO;
+global using System.Linq;
+global using System.Net.Http;
+global using System.Threading;
+global using System.Threading.Tasks;

src/OpenApi.Client.Mcp/Log.cs

@@ -0,0 +1,35 @@
+// This Source Code Form is subject to the terms of the MIT License.
+// If a copy of the MIT was not distributed with this file, You can obtain one at https://opensource.org/licenses/MIT.
+// Copyright (C) Leszek Pomianowski and OpenAPI Client Contributors.
+// All Rights Reserved.
+
+namespace OpenApi.Client.Mcp;
+
+internal static partial class Log
+{
+    private enum Event
+    {
+        FailedToFetchOpenApi = 042137,
+        FatalErrorWhileFetchingOpenApi,
+    }
+
+    [LoggerMessage(
+        EventId = (int)Event.FailedToFetchOpenApi,
+        EventName = nameof(Event.FailedToFetchOpenApi),
+        Level = LogLevel.Warning,
+        Message = "Failed to fetch OpenAPI document from \"{Url}\". Please check the URL and your network connection."
+    )]
+    public static partial void LogFetchingFailed(this ILogger logger, string url);
+
+    [LoggerMessage(
+        EventId = (int)Event.FatalErrorWhileFetchingOpenApi,
+        EventName = nameof(Event.FatalErrorWhileFetchingOpenApi),
+        Level = LogLevel.Error,
+        Message = "Fatal error while fetching OpenAPI document from \"{Url}\". Please check the URL and your network connection."
+    )]
+    public static partial void LogFetchingFailedWithError(
+        this ILogger logger,
+        Exception exception,
+        string url
+    );
+}

src/OpenApi.Client.Mcp/OpenApi.Client.Mcp.csproj

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+  <PropertyGroup>
+    <TargetFramework>$(CommonTargetFramework)</TargetFramework>
+    <UserSecretsId>47a6b027-b381-4465-8c68-1f63fc721408</UserSecretsId>
+    <DockerfileContext>..\..</DockerfileContext>
+    <ContainerDevelopmentMode>Fast</ContainerDevelopmentMode>
+    <DockerfileRunEnvironmentFiles>..\..\.env</DockerfileRunEnvironmentFiles>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="Microsoft.CodeAnalysis.Common" />
+    <PackageReference Include="ModelContextProtocol" />
+    <PackageReference Include="ModelContextProtocol.AspNetCore" />
+    <PackageReference Include="Microsoft.VisualStudio.Azure.Containers.Tools.Targets" />
+    <PackageReference Include="Microsoft.Extensions.Http.Resilience" />
+    <PackageReference Include="Microsoft.OpenApi" />
+    <PackageReference Include="Microsoft.OpenApi.YamlReader" />
+    <PackageReference Include="OpenTelemetry.Exporter.OpenTelemetryProtocol" />
+    <PackageReference Include="OpenTelemetry.Extensions.Hosting" />
+    <PackageReference Include="OpenTelemetry.Instrumentation.AspNetCore" />
+    <PackageReference Include="OpenTelemetry.Instrumentation.Http" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\OpenApi.Client.SourceGenerators\OpenApi.Client.SourceGenerators.csproj" />
+  </ItemGroup>
+</Project>

src/OpenApi.Client.Mcp/Program.cs

@@ -0,0 +1,68 @@
+// This Source Code Form is subject to the terms of the MIT License.
+// If a copy of the MIT was not distributed with this file, You can obtain one at https://opensource.org/licenses/MIT.
+// Copyright (C) Leszek Pomianowski and OpenAPI Client Contributors.
+// All Rights Reserved.
+
+WebApplicationBuilder builder = WebApplication.CreateBuilder(args);
+
+builder.Logging.AddConsole(consoleLogOptions =>
+{
+    // Configure all logs to go to stderr
+    consoleLogOptions.LogToStandardErrorThreshold = LogLevel.Trace;
+});
+
+#if DEBUG
+builder
+    .Services.AddOpenTelemetry()
+    .WithTracing(b => b.AddSource("*").AddAspNetCoreInstrumentation().AddHttpClientInstrumentation())
+    .WithMetrics(b => b.AddMeter("*").AddAspNetCoreInstrumentation().AddHttpClientInstrumentation())
+    .WithLogging()
+    .UseOtlpExporter();
+#endif
+
+builder.Services.AddTransient<IOpenApiService, OpenApiService>();
+
+builder.Services.AddHttpClient();
+
+ServerOptions serverOptions = new();
+IConfigurationSection section = builder.Configuration.GetSection("Server");
+section.Bind(serverOptions);
+
+string? mode = Environment.GetEnvironmentVariable("mode") ?? Environment.GetEnvironmentVariable("MODE");
+
+if (mode?.Contains("both", StringComparison.InvariantCultureIgnoreCase) ?? false)
+{
+    serverOptions.Mode = McpMode.Both;
+}
+else if (mode?.Contains("http", StringComparison.InvariantCultureIgnoreCase) ?? false)
+{
+    serverOptions.Mode = McpMode.Http;
+}
+
+IMcpServerBuilder mcpBuilder = builder.Services.AddMcpServer();
+
+if (serverOptions.Mode == McpMode.Both)
+{
+    _ = mcpBuilder.WithHttpTransport().WithStdioServerTransport();
+}
+else if (serverOptions.Mode == McpMode.Stdio)
+{
+    _ = mcpBuilder.WithStdioServerTransport();
+}
+else
+{
+    _ = mcpBuilder.WithHttpTransport();
+}
+
+_ = mcpBuilder.WithTools<OpenApiTools>();
+
+await using WebApplication app = builder.Build();
+
+if (serverOptions.Mode is McpMode.Http or McpMode.Both)
+{
+    app.MapMcp();
+}
+
+await app.RunAsync();
+
+return;

src/OpenApi.Client.Mcp/Properties/launchSettings.json

@@ -0,0 +1,14 @@
+{
+  "profiles": {
+    "ModelContextProtocol": {
+      "commandName": "Project",
+      "launchBrowser": false,
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development",
+        "OTEL_SERVICE_NAME": "sse-server",
+        "MODE": "Both"
+      },
+      "applicationUrl": "http://localhost:64622"
+    }
+  }
+}

src/OpenApi.Client.Mcp/Services/IOpenApiService.cs

@@ -0,0 +1,34 @@
+// This Source Code Form is subject to the terms of the MIT License.
+// If a copy of the MIT was not distributed with this file, You can obtain one at https://opensource.org/licenses/MIT.
+// Copyright (C) Leszek Pomianowski and OpenAPI Client Contributors.
+// All Rights Reserved.
+
+namespace OpenApi.Client.Mcp.Services;
+
+internal interface IOpenApiService
+{
+    /// <summary>
+    /// Creates an OpenAPI client from the specified URL address of the OpenAPI JSON file or Swagger-generated JSON.
+    /// </summary>
+    Task<string> CreateFromFileAsync(string address, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Retrieves a list of operations from the specified OpenAPI JSON file or Swagger-generated JSON.
+    /// </summary>
+    Task<string> GetOperationsAsync(string address, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Generates a curl command for a given operation ID from the OpenAPI specification.
+    /// </summary>
+    Task<string> GenerateCurlCommandAsync(
+        string address,
+        string operationId,
+        string? baseAddress,
+        CancellationToken cancellationToken = default
+    );
+
+    /// <summary>
+    /// Validates the OpenAPI document at the specified address and returns a string indicating the validation result.
+    /// </summary>
+    Task<string> ValidateDocumentAsync(string address, CancellationToken cancellationToken = default);
+}