dotnet-mcp-server

Create an internal sealed class with methods annotated [McpServerTool] and [Description], inject a typed HttpClient via the constructor, and register it with AddMcpServer().WithTools<T>() in Program.cs. Return Task<string> with serialized JSON rather than Task<object> to avoid JsonElement boxing issues.

Use a mock HttpMessageHandler that captures the request method, URI, and JSON body while returning a canned response. Construct the tool class directly with an HttpClient wrapping that handler, and cover non-success status codes with a single [Theory] using InlineData.

Yes, the ModelContextProtocol.AspNetCore package adds Streamable HTTP via WithHttpTransport and MapMcp, requiring the Web SDK. A dual-mode server selects transport from an env var with a case-insensitive comparison, since a bare == "http" check silently falls back to stdio for HTTP or Http.

A dropped .WithTools<T>() registration in Program.cs removes tools at runtime while class-level reflection tests stay green. Guard against this with a host-level test that enumerates the actually registered tool names, plus a live tools/list probe against the published binary after an initialize handshake.

The SDK only includes the exception message in the error result when the exception is McpException; other exceptions surface as a generic message. Throw McpException with a coded message or return a CallToolResult with IsError = true and explicit TextContentBlock content.

Yes, but parse-first with System.CommandLine and never invoke default actions, because help renders to stdout and would corrupt the JSON-RPC stream. Detect help via parseResult.Action is HelpAction and render to stderr with your own renderer.