# File-Based MCP Server Sample

This sample demonstrates how to create a complete MCP (Model Context Protocol) server using [.NET 10's file-based programs feature](https://learn.microsoft.com/dotnet/csharp/fundamentals/tutorials/file-based-programs). Unlike traditional .NET projects that require a `.csproj` file, file-based programs allow you to write and run complete applications in a single `.cs` file.

## Running the Sample

Simply run the Program.cs file directly:

```bash
./Program.cs
```

The server will start and listen for MCP messages on stdin/stdout (stdio transport).

## Testing the Server

You can test the server by using `@modelcontextprotocol/inspector`, any stdio-compatible client, or sending JSON-RPC messages to stdin.

### Using the Inspector

```bash
npx @modelcontextprotocol/inspector ./Program.cs
```

### Using STDIN

#### Initialize the server

```bash
echo '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test-client","version":"1.0"}}}' | ./Program.cs
```

#### List available tools

```bash
(
  echo '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test-client","version":"1.0"}}}'
  sleep 0.5
  echo '{"jsonrpc":"2.0","id":2,"method":"tools/list","params":{}}'
  sleep 1
) | ./Program.cs 2>/dev/null | grep '^{' | jq .
```

#### Call the echo tool

```bash
(
  echo '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test-client","version":"1.0"}}}'
  sleep 0.5
  echo '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"echo","arguments":{"message":"Hello, MCP!"}}}'
  sleep 1
) | ./Program.cs 2>/dev/null | grep '^{' | jq .
```

## Reference

- [File-Based Programs Tutorial](https://learn.microsoft.com/dotnet/csharp/fundamentals/tutorials/file-based-programs)
- [C# Preprocessor Directives for File-Based Apps](https://learn.microsoft.com/dotnet/csharp/language-reference/preprocessor-directives#file-based-apps)
- [Model Context Protocol Specification](https://modelcontextprotocol.io/specification/)