Function derive_input_schema 

pub fn derive_input_schema(
    params: &[ParamDef],
    described: &[(String, String)],
) -> Option<Value>

Build the input_schema object for one verb’s parameter list.

Returns None when any declared spelling has no mapping, so a verb is never published with a schema that quietly omits one of its parameters. A partial schema is worse than none: a driver would read it as complete.