Input parameters are easy enough to find, to borrow a query from another stack exchange answer:
select
'Parameter_name' = name,
'Type' = type_name(user_type_id),
'Proc_Name' = object_name(object_id),
'Length' = max_length,
'Prec' = case when type_name(system_type_id) = 'uniqueidentifier'
then precision
else OdbcPrec(system_type_id, max_length, precision) end,
'Scale' = OdbcScale(system_type_id, scale),
'Param_order' = parameter_id,
'Collation' = convert(sysname,
case when system_type_id in (35, 99, 167, 175, 231, 239)
then ServerProperty('collation') end)
from sys.parameters
However parameters declared within the procedure are not accessible this way, to find those parameters you need to search within the procedures themselves:
select OBJECT_NAME(id) as ProcName, SUBSTRING(text, CHARINDEX('Declare @',text), 250) as DeclaredVarables
from SYSCOMMENTS
where CHARINDEX('Declare @',text) > 0
order by OBJECT_NAME(id), CHARINDEX('Declare @',text)
Which will get you the procedure name and (hopefully) the relevant bits of the procedure. You may have to dial in the substring depending on coding standards, but that should give you a list of params declared within procedures.