Seting custom field in Youtrack Issue via API using Python

When i'm adding issue to YouTrack via Api using python (requests lib). everything works as expected. Code below:

postHeaders = {
    'Accept':'application/json',
    'Authorization':'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx',
    'Content-Type':'application/json'
    
}

postData = {
    'project':{'id':'0-5'},
    'summary':project_name,
    'description':description,

responsePost = requests.post("https://myCompany.youtrack.cloud/api/issues", headers=postHeaders, data=postData_json)

print(responsePost.content)

Than i made a custom field in Youtrack lets call it important_number.

When i add

"customFields":[
        { "name":"important_number","$type":"SimpleIssueCustomField","value":{"name":'123'}},
]

to my postData, as Youtrack documentation says i got error:

{"error":"server_error","error_description":"Tried to set object to field of primitive type"}'

I'm sure that the $type and name is correct because i querry the YT for that info and paste it in code.

I have tried changig type for every other posible there is, but nothing seems to work.