I have one request named as Stamp Request.
I want add value from Stamp customfield to description:

My script works very well it hasn't any error but it doesn't change issue description.
What did I forget?
import com.atlassian.jira.component.ComponentAccessor
//------------------------------------------------------
import com.atlassian.jira.bc.issue.IssueService
import com.atlassian.jira.issue.Issue
import com.atlassian.jira.issue.customfields.manager.OptionsManager
import com.atlassian.jira.issue.customfields.option.Options
import com.atlassian.jira.issue.fields.CustomField
import com.atlassian.jira.issue.IssueInputParameters
//------------------------------------------------------
def customFieldManager=ComponentAccessor.getCustomFieldManager()//Customfieldleri cagirmaq ucun customfieldManager yaradiriq
def customerRequestType=customFieldManager.getCustomFieldObjectByName("Customer Request Type")//Customer Request Type
Issue issue
def issCRT=issue.getCustomFieldValue(customerRequestType)
if(issue.getIssueType().name=="Stamp Request" && issCRT.toString()=="ad/badc2549-b904-4312-99a6-d7e2b9a0d31f")
{
def stamp=customFieldManager.getCustomFieldObjectByName("Stamp")//Stamp CustomField-ni tapir
def IssStamp=issue.getCustomFieldValue(stamp)//Issuedaki stampin qiymetin tapir
def issueInputParameters=IssueService.newIssueInputParameters()//Parametrler daxil etmek ucun
issueInputParameters.with//Parameter daxil edirik
{
description=description+IssStamp.toString()
}
}