Metadata discovery

[Ejb503]

Pre-submission Checklist

• I have verified this would not be more appropriate as a feature request in a specific repository
• I have searched existing discussions to avoid duplicates

Your Idea

I use metadata heavily, for tools/prompts and resources. This works to manage the state in the client.

A custom MCP client requires distinction between the core entities. For example, a delete_tool has entirely different handlers than a 'web_search' tool.

As an example, I find myself heavily using the following metadata (and much more).

Hidden: boolean -> Don't expose in client
Ignore: boolean -> human use only,
Title: string -> UI interface,
Description: string -> UI interface,

this helps me handle the use of tools differently within the client, for example I don't give access to my LLMs to dangerous tools, but I do provide a UI for human use within the client. There is also a distinction between descriptions for people and descriptions for LLMs. (NEVER USE THIS TOOL IS VERY DANGEROUS!!!) is not a human friendly title :)

This seems to me to be the intended use of Metadata, and it works very well.

From a spec point of view, my life would be improved by having a discovery mechanism and getters on the client (that could easily be typed), as I imagine that this Metadata implementation will repeated (in an opinionated way) in nearly every MCP client that is implemented.

Possibly enhancement might be Client<--Server discovery of _metadata types... i.e. Server strictly defines metadata for each entity.

This helps implement type-safe and reliable clients.

Scope

• Protocol Specification
• SDK Features
• Documentation
• Developer Experience
• Other

[nicarq]

Just thinking out loud, could also this be solved without any changes by grouping them through MCP Server proxies? so you have a specific MCP Server (proxy) for each one of those categories

[Ejb503]

I 100% can solve it (I used shared types for servers and clients), it's not an impossible challenge by any means.

However, I do wonder if life could be made a bit easier in terms of discovery. Not critical, perhaps a quality of life enhancement?

Also feel like this would be more of a problem for a typical scenario where client and server are "alien" and don't have trusted middleware.