Added changes to set McpServerOptions.Instructions in HTTPS/SSE mode.

[anushakolan]

Why make this change?

Closes #3283

runtime.mcp.description was configured, but MCP HTTP/SSE initialize did not return it as instructions. This made the engine behavior inconsistent with expected MCP initialization output.

Related discussion: #3282

What is this change?

• Wired runtime MCP description into MCP server options for HTTP/SSE initialization:

  • runtime.mcp.description -> ServerInstructions
  • Files updated:
    • src/Azure.DataApiBuilder.Mcp/Core/McpServiceCollectionExtensions.cs
    • src/Azure.DataApiBuilder.Mcp/Core/McpServerConfiguration.cs

• Added/updated regression coverage for initialize response instructions:

  • src/Service.Tests/Configuration/ConfigurationTests.cs
  • Test: TestMcpInitializeIncludesInstructionsFromRuntimeDescription

How the bug was simulated:

• Reverted the MCP wiring changes and called MCP initialize; result.instructions was missing.

How it was verified after fix:

• Re-applied the wiring, called MCP initialize again, and confirmed result.instructions is present.

How was this tested?

• Integration Tests
• Unit Tests

Ran:

• dotnet test src/Service.Tests/Azure.DataApiBuilder.Service.Tests.csproj --filter "FullyQualifiedName~ConfigurationTests.TestMcpInitializeIncludesInstructionsFromRuntimeDescription" -v minimal

Sample Request(s)

MCP initialize request (HTTP):

curl -i -X POST http://localhost:5000/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{
    "jsonrpc":"2.0",
    "id":1,
    "method":"initialize",
    "params":{
      "protocolVersion":"2025-03-26",
      "capabilities":{},
      "clientInfo":{"name":"manual-test","version":"1.0.0"}
    }
  }'

Expected response snippet after fix:

{
  "result": {
    "instructions": "Use SQL tools to query the database."
  }
}

[Copilot]

Pull request overview

This PR aligns MCP HTTP/SSE initialization behavior with the stdio transport by propagating runtime.mcp.description into the MCP initialize response’s instructions field, and adds a regression test to prevent regressions.

Changes:

• Pass runtime.mcp.description into MCP server configuration during DI setup.
• Set MCP server options (ServerInstructions) so HTTP/SSE initialize includes instructions.
• Add an MSSQL integration test that calls MCP initialize and asserts result.instructions is present (with helper logic to parse JSON vs SSE responses).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/Azure.DataApiBuilder.Mcp/Core/McpServiceCollectionExtensions.cs	Passes runtime MCP description into MCP server configuration during service registration.
src/Azure.DataApiBuilder.Mcp/Core/McpServerConfiguration.cs	Adds an instructions parameter and wires it to MCP server options used by HTTP/SSE initialize.
src/Service.Tests/Configuration/ConfigurationTests.cs	Adds a regression test + helper to invoke MCP initialize and validate returned instructions.

[Copilot]

GetMcpInitializeResponse duplicates the initialize request payload + retry loop logic already implemented in GetMcpResponse. This increases the chance the two helpers drift (e.g., protocolVersion/capabilities/headers/retry conditions). Consider extracting a shared helper for building/sending the MCP initialize request (and optionally returning the response body) to keep behavior consistent.

[Copilot]

Inside the retry loop, HttpRequestMessage/HttpResponseMessage are created repeatedly but never disposed. In long/parallel test runs this can retain resources longer than needed; prefer wrapping both in using (and reading content before disposal) within each iteration.

Suggested change

	HttpRequestMessage mcpRequest = new(HttpMethod.Post, mcp.Path)
	{
	Content = JsonContent.Create(payload)
	};
	mcpRequest.Headers.Add("Accept", "application/json, text/event-stream");
	HttpResponseMessage mcpResponse = await httpClient.SendAsync(mcpRequest);
	using HttpRequestMessage mcpRequest = new(HttpMethod.Post, mcp.Path)
	{
	Content = JsonContent.Create(payload)
	};
	mcpRequest.Headers.Add("Accept", "application/json, text/event-stream");
	using HttpResponseMessage mcpResponse = await httpClient.SendAsync(mcpRequest);

[Copilot]

ExtractJsonFromSsePayload only returns a single data: line that starts with {. SSE events can legally split a JSON payload across multiple data: lines (which should be concatenated with newlines). Consider accumulating consecutive data: lines for the event and then parsing the combined string to avoid flaky parsing if the transport changes formatting/chunking.

Suggested change

	foreach (string line in ssePayload.Split('\n'))
	{
	string trimmed = line.Trim();
	if (trimmed.StartsWith("data:", StringComparison.OrdinalIgnoreCase))
	{
	string data = trimmed.Substring("data:".Length).Trim();
	if (!string.IsNullOrWhiteSpace(data) && data.StartsWith('{'))
	{
	return data;
	}
	}
	}
	return string.Empty;
	List<string> eventDataLines = new();
	static string GetJsonPayload(List<string> dataLines)
	{
	if (dataLines.Count == 0)
	{
	return string.Empty;
	}
	string combinedPayload = string.Join("\n", dataLines);
	return !string.IsNullOrWhiteSpace(combinedPayload) && combinedPayload.TrimStart().StartsWith('{')
	? combinedPayload
	: string.Empty;
	}
	foreach (string rawLine in ssePayload.Split('\n'))
	{
	string line = rawLine.TrimEnd('\r');
	if (string.IsNullOrWhiteSpace(line))
	{
	string jsonPayload = GetJsonPayload(eventDataLines);
	if (!string.IsNullOrEmpty(jsonPayload))
	{
	return jsonPayload;
	}
	eventDataLines.Clear();
	continue;
	}
	if (line.StartsWith("data:", StringComparison.OrdinalIgnoreCase))
	{
	string data = line.Substring("data:".Length);
	if (data.StartsWith(' '))
	{
	data = data.Substring(1);
	}
	eventDataLines.Add(data);
	}
	}
	return GetJsonPayload(eventDataLines);