To assign variables to another variable, do not wrap the variable in quotes:
{assign var="Counted" value=$var.description|unescape|count_characters}
If you are passing an array to a function, you might have to use the @
operator:
{assign var="Counted" value=$var.description|@unescape|@count_characters}
If you need to include text AND a variable, use quotes and wrap the variable in "`" ("backticks")
{assign var="Counted" value="`$var.description` plus other text"|unescape|count_characters}
As you see, no matter how I am assigning the variable, I do not put the names of functions within quotes. The pipe-function_name format belongs outside any quoted text in all cases.