Are "server instructions" actually supported?

[ouvreboite]

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• I have checked that this question would not be more appropriate as an issue in a specific repository
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Question Category

• Protocol Specification
• SDK Usage
• Server Implementation
• General Implementation
• Documentation
• Other

Your Question

I see that there is a way to define "instructions" for the server.

builder.Services.AddMcpServer(serverOptions =>
{
 serverOptions.ServerInstructions = "Use tool A but not tool B";
})

I can see the instructions in the response to the initialize request (using MCP Inspector), but my instructions are ignored by clients (Claude Desktop and VSCode Copilot's agent).
I'm also struggling to see any mention of "instructions" on https://modelcontextprotocol.io/specification/2024-11-05/server (even if it's present on the official schema).

So do you know if this feature is actually supported by MCP clients?