[Bug]: Server `instruction` not set properly in the engine.

[JerryNixon]

What?

The runtime.mcp.description config value is read into McpRuntimeOptions.Description and emitted as instructions in the stdio server's HandleInitialize, but the HTTP/SSE transport configured in McpServerConfiguration.cs never sets McpServerOptions.Instructions. MCP clients connecting over HTTP/SSE never receive instructions in the initialize response.

Suggestion

services.PostConfigure<McpServerOptions>(options =>
{
    options.ServerInfo = new() { Name = McpProtocolDefaults.MCP_SERVER_NAME, Version = McpProtocolDefaults.MCP_SERVER_VERSION };
    options.Capabilities ??= new();
    options.Capabilities.Tools ??= new();
    
    // Read the description from runtime config and set it as instructions
    // (This needs access to RuntimeConfigProvider, so the implementation 
    //  would need to use services.AddOptions<McpServerOptions>() with a 
    //  configure callback that resolves from the service provider)
    options.Instructions = runtimeConfig.Runtime?.Mcp?.Description;
});

Also

Additionally, the description property is missing from the mcp object in schemas/dab.draft.schema.json, so configs using it fail schema validation since that object has "additionalProperties": false. #3282

[JerryNixon]

I am not sure the SDK supported this when the original PR was merged.

[JerryNixon]

Using curl against a HTTP MCP endpoint

$ curl -X POST https://ca-dab-api.agreeablesky-bf194cf3.westus2.azurecontainerapps.io/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -H "MCP-Protocol-Version: 2024-11-05" \
  -d '{
    "jsonrpc":"2.0",
    "id":1,
    "method":"initialize",
    "params":{
      "protocolVersion":"2024-11-05",
      "clientInfo":{"name":"curl","version":"1.0"},
      "capabilities":{}
    }
  }'

If DAB is setting the server instruction correctly you should see something like

{
    "result": {
        "protocolVersion": "2024-11-05",
        "capabilities": {
            "logging": {},
            "tools": {}
        },
        "serverInfo": {
            "name": "SQL MCP Server",
            "version": "2.0.0"
        },
       "instructions": "Use SQL tools to query the database." // here (this is what SHOULD be)
    },
    "id": 1,
    "jsonrpc": "2.0"
}

right now this is all we get

{
    "result": {
        "protocolVersion": "2024-11-05",
        "capabilities": {
            "logging": {},
            "tools": {}
        },
        "serverInfo": {
            "name": "SQL MCP Server",
            "version": "2.0.0"
        }
                         // no instructions
    },
    "id": 1,
    "jsonrpc": "2.0"
}

This could be automated in a test

var client = await McpClient.CreateAsync(
    new HttpClientTransport(new HttpClientTransportOptions
    {
        Endpoint = new Uri("http://localhost:5000/mcp")
    }));

var info = await client.InitializeAsync();
Console.WriteLine(info.Instructions);

[Aniruddh25]

The SDK did not support it in the HTTP based MCP server. Thats why it was not added in the original PR which implemented the description