Proposal: reachable client capabilities in Server Session

[ardaguclu]

Is your feature request related to a problem? Please describe.
MCP Servers may want to check the capabilities of the client and decide actions based on it. For instance, MCP Server checks whether client supports elicitation or not. If client supports this, MCP Server initiates an elicitation request.

Describe the solution you'd like
Client capabilities are already embedded and stored in

go-sdk/mcp/server.go

Line 523 in 78a66a4

initializeParams *InitializeParams

ServerSession. However, MCP Servers can't access to this field. I recommend to introduce a new function such as GetInitializeParams, or whatever that is used in tool calls to check the client capabilities.

Describe alternatives you've considered
Nothing comes to my mind as an alternative. But I appreciate if there is already a way and we can close this issue.

Additional context
I've opened this mark3labs/mcp-go#491 to embed capabilities in session. However, those fields are already stored in here. We just need a way to expose it.

[samthanawalla]

Same problem as #166, exposing InitializeParams seems like the solution for ServerSession and exposing InitializeResult is the solution for ClientSession.

[findleyr]

@samthanawalla want to pick this up, since you reviewed the opposite direction?