Describe the bug
The MCP documentation states that we can declare annotations in the @mcp.tool() decorator with the Python SDK, however this functionality is not present in the code.

Documentation:
https://modelcontextprotocol.io/docs/concepts/tools#python

Location in code base:
https://github.com/modelcontextprotocol/python-sdk/blob/main/src/mcp/server/fastmcp/server.py#L262

To Reproduce
Steps to reproduce the behavior:

• Decorate a function with <fastMCP server name>.tool(annotations={"example":"example_val"})
• Run the MCP Server in Claude Desktop
• This should populate the logs with the following error: TypeError: FastMCP.tool() got an unexpected keyword argument 'annotations'

Expected behavior
This should be valid and add annotation data to the tool.

Desktop (please complete the following information):

• OS: MacOS
• Version 15.3.2
• Python 3.12.7
• mcp[cli] 1.6.0