Why methods tagged with [McpServerPromptAttribute] in class tagged with [McpServerPromptTypeAttribute] are never invoked by the Copilot agent ?

[ndepend]

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Discussion Topic

For our MCP server we have prompts to guide the Copilot agent. Why static public methods tagged with [McpServerPromptAttribute] in class tagged with [McpServerPromptTypeAttribute] are never invoked by the Copilot agent? As far as I understand prompts are part of the MCP protocol like tools.

Also how to differentiate an identity prompt from a guideline prompt.

Thank you

Btw Copilot gave me this answer:

The method tagged with McpServerPromptAttribute is intended for use within your own application's infrastructure—such as your chat system, UI, or backend logic—to define and describe prompt types for NDepend MCP Server actions. As an external agent, I do not invoke C# methods or attributes directly; instead, I interact with the NDepend MCP Server via its API/tooling interface to perform analysis and return results.

[mikekistler]

According to the MCP Spec:

Prompts are designed to be user-controlled, meaning they are exposed from servers to clients with the intention of the user being able to explicitly select them for use.

This is different from tools and resources which are intended to be provided to the LLM in the context window. So it is not surprising that the LLM does not request any prompts -- it likely knows nothing about them.

[PederHP]

In addition to this, prompts are not the right choice of capability to help guide the model. If you have tools not being called or called incorrectly - then improving the description and/or providing examples is the way to improve this. Make sure the tool name, description and parameter names and descriptions are good. Running evals can help you figure out what works best with a given model (e.g. for GitHub Copilot it makes sense to run evals with the default models and the most popular premium models).

You can also provide guidance in the instructions property of the server capabilities, but not all clients support this. GitHub Copilot does support this, so I would recommend trying it out if you need guidance on how to use multiple tools together or some similar information not well suited for an individual tool description.

Prompts are like message templates. Many clients don't support prompts, and those that do tend to treat them like a prompt library or slash-commands for the server.

[ndepend]

Thanks @PederHP and @mikekistler, all these was not obvious from the [McpServerPrompt*Attribute] documentation.

@PederHP you mentioned instructions property, could you elaborate on this concept and its implementation in
modelcontextprotocol/csharp-sdk, I dind't find any file containing Instruction

Thank you