How to declare a property in elicitation form as not required?

[pommfresser]

Hi, I'm using fastmcp to build a mcp server but I'm struggling to declare properties in elicitation forms as not required.

Sample code:

from typing import Optional

from fastmcp import Context
from fastmcp.server import FastMCP
from pydantic import BaseModel, Field

mcp = FastMCP("Test")

async def approval_form(ctx: Context):
    class Test(BaseModel):
        name: str = Field(description="Enter your name")
        description: Optional[str] = Field(description="Description for text")
    result = await ctx.elicit(
        message="Test form",
        response_type=Test,
    )
    if result.action == "accept":
        return result.data, True
    else:
        return None, False

@mcp.tool("TestTool")
async def test_tool(ctx: Context, name: str):
    data, approval = await approval_form(ctx)
    if not approval:
        return "User approval failed"
    return {"Status": "Success", "Name": data.name}

if __name__ == "__main__":
    mcp.run(
        transport="http",
        host="127.0.0.1",
        port=8080,
        path="/test"
    )

The following exception is thrown if I use the tool:

TypeError: Elicitation schema field 'description' has union type
                             'null' which is not a primitive type. Only {'boolean', 'integer',
                             'number', 'string'} are allowed in elicitation schemas.

I wasn't able to get this example running and didn't find any documentation regarding this issue. Maybe someone can help me fix this problem.

Thanks in advance!