Tharga.Mcp

Foundation package for MCP (Model Context Protocol) infrastructure in the Tharga ecosystem. Wraps the official ModelContextProtocol C# SDK with a Tharga-flavored registration pattern so downstream provider packages (Tharga.MongoDB.Mcp, Tharga.Platform.Mcp, etc.) compose cleanly inside a single AddThargaMcp(...) callback.

Tharga.Mcp itself has no dependency on any other Tharga package — the auth/scope/audit integration lives in Tharga.Platform.Mcp (Phase 1).

Install

dotnet add package Tharga.Mcp

Minimal usage

using Tharga.Mcp;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddThargaMcp(mcp =>
{
    mcp.Services.AddMcpServer().WithTools<HelloTools>();
});

var app = builder.Build();
app.UseThargaMcp();
app.Run();

UseThargaMcp() exposes the MCP endpoint at ThargaMcpOptions.EndpointBasePath (default /mcp). It also honors ThargaMcpOptions.RequireAuth (default true) — when set, the endpoint calls .RequireAuthorization() and requires the consumer to wire UseAuthorization() + an authentication scheme in the pipeline. Set mcp.Options.RequireAuth = false during registration to expose the endpoint anonymously.

An [Obsolete] MapMcp() alias still works for one release cycle but will be removed — update when you can.

Defining tools

Any class tagged with [McpServerToolType] exposing [McpServerTool] methods is recognised by the SDK:

[McpServerToolType]
public sealed class HelloTools
{
    [McpServerTool, Description("Returns a greeting for the given name.")]
    public string Greet([Description("The name to greet.")] string name)
        => $"Hello, {name}!";
}

Provider contracts

Tharga.Mcp also defines IMcpResourceProvider and IMcpToolProvider with per-scope registration (User, Team, System). This is the path for packages that need dynamic tools/resources — where the set of tools is known only at runtime (e.g. one MCP resource per MongoDB collection).

public sealed class TimeToolProvider : IMcpToolProvider
{
    public McpScope Scope => McpScope.System;

    public Task<IReadOnlyList<McpToolDescriptor>> ListToolsAsync(IMcpContext context, CancellationToken ct)
        => Task.FromResult<IReadOnlyList<McpToolDescriptor>>(
            [new McpToolDescriptor { Name = "time_now", Description = "Current UTC time." }]);

    public Task<McpToolResult> CallToolAsync(string name, JsonElement args, IMcpContext context, CancellationToken ct)
        => Task.FromResult(new McpToolResult
        {
            Content = [new McpContent { Text = DateTimeOffset.UtcNow.ToString("O") }],
        });
}

builder.Services.AddThargaMcp(mcp =>
{
    mcp.AddToolProvider<TimeToolProvider>();
});

Provider packages expose an extension method on IThargaMcpBuilder so consumers can compose them inside the same callback:

builder.Services.AddThargaMcp(mcp =>
{
    mcp.AddMongoDB();   // from Tharga.MongoDB.Mcp
    mcp.AddPlatform();  // from Tharga.Platform.Mcp
    mcp.AddToolProvider<MyCustomProvider>();
});

The two paths (attribute-based [McpServerTool] and contract-based IMcpToolProvider) work side by side — use attributes for statically-declared tools, providers for dynamic or programmatically-generated tools. Scope filtering (/mcp/me, /mcp/team, /mcp/system) activates in Phase 1 once Tharga.Platform.Mcp populates IMcpContextAccessor.Current from the authenticated request.

Endpoint scopes

The master plan defines three scopes — User (/mcp/me), Team (/mcp/team), System (/mcp/system). Phase 0 ships a single endpoint (/mcp) that exposes registered tools and resources filtered by a scope hierarchy: a caller at System sees User + Team + System providers; Team sees User + Team; User sees only User. The caller's effective scope is read from IMcpContextAccessor.Current (populated by Tharga.Platform.Mcp from the authenticated principal, or left anonymous in Phase 0). When no context is populated, every provider is visible. The three-endpoint split is deferred — see the master plan decision 2026-04-18.

Sample

Runnable end-to-end sample lives under Sample/Tharga.Mcp.Sample/. Start it and connect with @modelcontextprotocol/inspector:

cd Sample/Tharga.Mcp.Sample
dotnet run
# in another terminal:
npx @modelcontextprotocol/inspector http://localhost:5138/mcp

License

MIT. See LICENSE.