How to add epic link in jira api

[yaogang xu]

This is my request

{
"fields": {
"project": {
"id": "1111"
},
"issuetype": {
"name": "test"
},
"priority": {
"name": "test"
},
"labels": ["Chandler"],
"customfield_10012": {
"id": "test"
},
"fixVersions": [{
"name": "11111"
}],
"summary": "test",
"customfield_14003": {
"name":"Checkout"
},
"description": "test"
}
}

customfield_14003 is epic link field,  I tried to pass its value in the request, but I got error

'String value expected as the Epic Key.' Is there anyone knows the correct format of passing epic link in jira api?

[Vladimir Kibe]

You must enter string value:

"customfield_10006": "issuekey"