feat: support setting title and description for server

[the-ayyi]

This PR is based on another draft PR.

Core Type Changes

• src/mcp/types.py: Added description: str | None field to Implementation class

Server Model Changes

• src/mcp/server/models.py: Added title and description fields to InitializationOptions

Low-Level Server Changes

• src/mcp/server/lowlevel/server.py:
  • Updated Server.__init__() to accept title and description parameters
  • Updated create_initialization_options() to include these fields

Session Changes

• src/mcp/server/session.py: Updated to pass title and description to serverInfo in InitializeResult

FastMCP Changes

• src/mcp/server/fastmcp/server.py:
  • Added title and description parameters to __init__()
  • Added @property methods for read access
  • Passes values through to underlying MCPServer

Github-Issue:#1783

Motivation and Context

The MCP specification defines an Implementation schema (used for both clientInfo and serverInfo in initialization) that includes both title and description fields for providing human-readable metadata to MCP hosts. However, the Python SDK had several gaps:

1. Missing description field: While Implementation inherited title from BaseMetadata, it was missing the description field entirely, even though the MCP spec supports it.

2. Server initialization limitations: The server only accepted InitializationOptions which didn't support setting title or description, making it impossible for servers to provide this metadata to clients.

3. Inconsistent support: Clients could at least set title via clientInfo (an Implementation object), but servers had no way to set either field.

This PR addresses the server-side implementation, allowing MCP servers to provide human-readable titles and descriptions that can be displayed by MCP hosts in their user interfaces, improving the user experience when working with multiple MCP servers.

How Has This Been Tested?

Tests

• tests/server/test_session.py: Added test for low-level server title/description
• tests/server/fastmcp/test_server.py: Added tests for FastMCP with and without title/description

Breaking Changes

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context