What is Rscg Openapi2mcp

RSCG_OpenApi2MCP is a .NET library that facilitates the generation of MCP files from OpenAPI specifications, streamlining the integration of APIs within the MCP environment.

Use cases

Use cases include building RESTful APIs that need to be documented with OpenAPI, generating MCP files for service-oriented architectures, and facilitating API communication in microservices.

How to use

To use RSCG_OpenApi2MCP, include the necessary NuGet packages in your project file, configure the services in program.cs, and build your project twice to generate the OpenAPI spec and the corresponding MCP files.

Key features

Key features include automatic generation of OpenAPI specifications, seamless integration with ASP.NET Core applications, and the ability to generate MCP files in a specified output directory.

Where to use

RSCG_OpenApi2MCP can be used in software development projects that require API management and integration within the MCP framework, particularly in enterprise applications.

RSCG_OpenApi2MCP

.NET Open API to MCP

How it works

The Microsoft.Extensions.ApiDescription.Server generates on build the OpenAPI spec for the API. This is then used to generate the MCP files.
The OpenAPI spec is generated in the obj folder. The MCP files are generated in the $(BaseIntermediateOutputPath)\GX\ folder.

Installation

Mandatory NuGet packages

Add this to the csproj

<ItemGroup>
     <PackageReference Include="RSCG_OpenApi2MCP" Version="9.2025.410.706" OutputItemType="Analyzer"  />
</ItemGroup>

Ensure also that you have the following in your csproj:

 <PropertyGroup>	
    <PackageReference Include="ModelContextProtocol" Version="0.1.0-preview.4" />
    <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="9.0.3" />
    <PackageReference Include="Microsoft.Extensions.ApiDescription.Server" Version="9.0.3">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>

 </PropertyGroup>

This is optional, but allows you to see what is generated for the MCP to work.

<PropertyGroup>
    <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>
    <CompilerGeneratedFilesOutputPath>$(BaseIntermediateOutputPath)\GX</CompilerGeneratedFilesOutputPath>
</PropertyGroup>

What to add to program.cs

builder.Services.AddOpenApi();
builder.Services.AddMcpServer().WithToolsFromAssembly();

builder.Services.AddHostedService<myServerAddress>();
//code

app.MapOpenApi();
app.UseOpenAPISwaggerUI();
app.MapMcpSse();

app.MapGet("/EchoWorld", (string id) => $"Hello World {id}!")
    .WithSummary("summary Echo the id")
    .WithDescription("description Echo the id")
    ;

Important notes

Every time that you want to have mcp files , please build 2 times in order to generate the correct MCP files. The first time the OpenAPI spec is generated, the second time the MCP files are generated. This is because the MCP files are generated from the OpenAPI spec.