Add Icon Support to Implementation (ServerInfo)

[aka-bk]

Add Icon Support to Implementation (ServerInfo)

Summary

Request to add icon support to the C# SDK's Implementation class to match the MCP specification and bring feature parity with other official SDKs (TypeScript, Python).

Problem

Currently, the C# SDK's Implementation class only supports Name and Version properties. When MCP servers are displayed in clients like Claude Desktop, they show default or technology-based icons (e.g., Microsoft logo for .NET servers) instead of custom branding.

Background

Icon support was added to the MCP specification via Issue #973 and is already implemented in:

• TypeScript SDK: ✅ Implemented
• Python SDK: ✅ Implemented
• C# SDK: ❌ Not yet implemented

Proposed Solution

Add optional Icons and WebsiteUrl properties to the Implementation class to match the spec.

Expected API

public class Implementation
{
    public required string Name { get; init; }
    public required string Version { get; init; }
    public Icon[]? Icons { get; init; }           // NEW
    public string? WebsiteUrl { get; init; }      // NEW
}

public class Icon
{
    public required string Src { get; init; }     // URL or data URI
    public string? MimeType { get; init; }
    public string[]? Sizes { get; init; }         // e.g., ["48x48", "96x96", "any"]
}

Usage Example

builder.Services.AddMcpServer()
    .WithHttpTransport()
    .WithToolsFromAssembly()
    .WithServerInfo(new Implementation
    {
        Name = "MCP Server Name",
        Version = "1.0.0",
        Icons = new[]
        {
            new Icon
            {
                Src = "https://example.com/logo.png",
                MimeType = "image/png",
                Sizes = new[] { "64x64" }
            }
        },
        WebsiteUrl = "https://example.com/docs"
    });

TypeScript SDK Reference

The TypeScript SDK implementation can be found at:
https://github.com/modelcontextprotocol/typescript-sdk/blob/main/src/types.ts

export const IconSchema = z.object({
    src: z.string(),
    mimeType: z.optional(z.string()),
    sizes: z.optional(z.array(z.string()))
}).passthrough();

export const ImplementationSchema = BaseMetadataSchema.extend({
    version: z.string(),
    websiteUrl: z.optional(z.string())
}).merge(IconsSchema);

export const IconsSchema = z.object({
    icons: z.array(IconSchema).optional()
}).passthrough();

Benefits

1. Visual Identity: Servers can display custom branding in MCP clients
2. Better UX: Users can quickly identify tools by their icons
3. Feature Parity: Aligns C# SDK with TypeScript and Python SDKs
4. Spec Compliance: Implements the full MCP specification

Use Case

We're building an enterprise MCP server for our organization. Currently, Claude Desktop displays the Microsoft logo for our .NET-based server. We'd like to display our company logo instead to help users visually identify our organizational tools.

Additional Context

• MCP Specification Issue: SEP-973: Expose additional metadata for Implementations, Resources, Tools and Prompts modelcontextprotocol#973
• Current C# SDK Version: 0.4.0-preview.2
• Icon formats should support: PNG, JPEG, SVG, WebP
• Icons can be URLs or base64 data URIs

Willing to Contribute

I'm interested in contributing a PR for this feature if the maintainers are open to it.

[stephentoub]

This was already added.
#802