Error while POST operation using oData exit operation

Hi All,

Below is the procedure I have which is used in oData exit operation

PROCEDURE "Tool::UserTableProcedure"(in row "Tool::User.insert", out message nvarchar(256))
   LANGUAGE SQLSCRIPT
   SQL SECURITY INVOKER
   AS
BEGIN
declare fn nvarchar(100);
declare ln nvarchar(100);
declare age integer;
    
select "fname","lname","ag" into fn,ln,age from :row;
insert into "Tool::User.insert" values (:fn,:ln,:age);

message:= 'Successfully inserted';
END;

While running the application, POST operation is not working as I'm getting the following error

"cannot read property 'mediatype' of null200,OK,An error occurred"

What could be the problem here? Below is my oData call

service{
"Tool.views::joinhb.view" as "user" keys("fname","lname")
create using "Tool::UserTableProcedure";
}