Derive Macro ToolName 

#[derive(ToolName)]
{
    // Attributes available to this derive:
    #[tool_name]
}

Derive agent_sdk::ToolName (plus the Serialize / Deserialize it requires) for an enum, removing the marker-impl boilerplate.

By default variants serialize as snake_case (matching the SDK’s built-in PrimitiveToolName). Override with #[tool_name(rename_all = "...")].