SkillFoxx

Nullable.Extended MCP

An MCP server and skill that find unjustified null-forgiving operators in C# solutions and steer toward code fixes.

  • 62 ★ on the repository
  • Last commit
  • MIT
MCP server

Minimal access

Why this level

  • The server reads solution source code and changes nothing itself, the agent makes the edits.
All reasons and checks

tom-englert/nullable.extendedAuthor:tom-englert

Install

Manual install

dotnet tool install -g Nullable.Extended.Mcp

No-install option: `dnx Nullable.Extended.Mcp --yes` in the MCP configuration.

Access and checks

How we review

Minimal accessThe tool runs nothing and makes no network calls.

  • The server reads solution source code and changes nothing itself, the agent makes the edits.

This is third-party code. Review the repository files before installing.

What it does

The Nullable.Extended project bundles three tools for working with nullable reference types in C#. A Roslyn analyzer as a NuGet package warns about every null-forgiving `!` operator without justification, a Visual Studio extension lists all such places in a solution and finds redundant ones, and the `Nullable.Extended.Mcp` MCP server helps an AI assistant find unjustified operators in large solutions project by project and without a build. The accompanying `nullable-extended` skill teaches the agent to fix the code first and use a `// ! reason` comment above the line only as a last resort. If the skill is not installed, the server sends the client a short version of the workflow on connection. It suits GitHub Copilot, Claude and other MCP clients.

Who it is for. C# developers with nullable types turned on whose large solutions have piled up `!` operators with no explanation.

Good fit when

  • A solution with dozens of projects needs every unjustified `!` found.
  • The agent should fix code so the null-forgiving operator is no longer needed.
  • Remaining `!` operators should get a `// !` comment with the reason.
  • A check on suppressions is introduced to the CI build as a warning.

Not a fit when

  • The project uses another language or has nullable types disabled.
  • There is no .NET 10 SDK, which is needed to launch the server with `dnx`.
  • You only want to silence warnings with no explanation.

Example request

Find unjustified null-forgiving operators in the solution, fix the code where possible and add reason comments for the rest.

MCP

Transport
stdio
Authentication
not required

Limitations

Running the MCP server needs the .NET 10 SDK or newer: `dnx` downloads and starts it on demand. The server finds operators without a build, so it knows nothing about semantic type errors. The skill and server suggest fixes but the decision stays with the developer and a justification comment does not replace a code fix. The analyzer and Visual Studio extension install separately and the MCP tools and parameters are described in `Documentation/McpServer.md`. The last commit was in November 2026.

How to disable. Remove the `Nullable.Extended.Mcp` entry from the MCP configuration, for example `.vscode/mcp.json`. Remove the skill from the skills directory and the global tool with `dotnet tool uninstall -g Nullable.Extended.Mcp`.

FAQ

How do I connect the MCP server?

Add a stdio server to the client configuration with the `dnx` command and arguments `Nullable.Extended.Mcp --yes`. The .NET 10 SDK is required.

Can the server be installed globally?

Yes: `dotnet tool install -g Nullable.Extended.Mcp`, then use the command `nullable-extended-mcp` in the configuration.

How do I install the skill?

Run `gh skill install tom-englert/Nullable.Extended nullable-extended` or `npx skills add tom-englert/Nullable.Extended`.

What does a justification comment look like?

One or more lines above the statement, the first starting with `// ! ` followed by the reason.

Is a solution build needed?

No, the server finds operators without a build, project by project.

Discussion

No questions or reviews yet.

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README in short

The README covers the problem of redundant null-forgiving operators, justification comments, the Roslyn analyzer, the Visual Studio extension and an AI assistants section with server registration and skill installation.

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